Comparison Study of Four Popular Lighting Simulation Software Programs

A Comparison Study of Four Popular Lighting Simulation Software Programs

MSc Dissertation By Peter Byrne B.Eng (Tech) Student Number 1041240

Brunel University Building Services Engineering with Sustainable Energy

Dissertation Tutor: Dr. Cosmin Ticleanu

September 2014

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Abstract The use of lighting simulation software is commonplace amongst professionals concerned with predicting the illuminance within buildings and for external environments. There are currently in excess of thirty different programs which provide this type of simulation to a lesser or greater degree. Although numerous programs exist, the mathematical algorithms used by most rely on either Ray-tracing or Radiosity methods to solve the global illumination equation.

Dialux, Relux, AGI32 and Radiance are amongst the most popularly used programs for lighting simulation. The results of an online survey completed by 129 respondents from forty five different countries confirm that Dialux is the most widely used and the most wellknown out of all programs. Its use is most prevalent in Europe and the program is most used by engineers. However, the analysis suggests that the more experienced user tends to favour AGI32 or others.

Each of the software programs has their photometric results compared for a series of scenarios. The scenarios include a daylight only scene, daylight and reflected artificial light scene and a reflected artificial only light scene. Each scene is constructed in a real test room where actual photometric results are recorded. The simulated results are compared to that of the actual results to highlight the extent of the differences between these values.

The results suggest that Radiance, Relux and AGI32 are all capable of simulating scenes encompassing a daylight component with Radiance producing the closest results when compared to measured values. The simulated results from Dialux deviate significantly from all other programs and measured values. In contrast, Dialux produces the closest results to measured values when simulating a scene with only reflected artificial light. All other programs are also within reasonable levels for this scene. No sound explanation for the Dialux deviation is established.

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Although aspects of the simulation comparisons' conclusions are supported by previous studies, it is felt that this study suffers from too great a margin of error to be able to confidently validate the photometric simulation abilities of these programs. However the results do indicate that significant deviations can occur in certain scene types using widely used and popular software.

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Acknowledgments This dissertation would not have been possible without the support of a number of people.

Firstly, I would like to thank my parents for always supporting me in every decision I have ever made, without this support I would have not been able to achieve the things I have.

I would also like to thank my wife Aisling whose idea it was so many years ago to return to my studies and who has always shown confidence in me and shown me that I can do anything I set my mind to. I would also like to thank her and my son Myles for putting up with all the missing hours on the weekends while I was preparing this work.

I would like to thank my dissertation tutor Dr. Cosmin Ticleanu for providing the much needed support, time and valuable feedback to complete this work within the allocated time. In addition, I am also very grateful to my course administrators Mary Bridge and Marie Lateo who have always provided the support and assistance whenever required.

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Table of Contents Chapter 1 Introduction ........................................................................................................................... 9 Introduction ........................................................................................................................................ 9 Background to the Project .................................................................................................................. 9 Selection of Software for this study.................................................................................................. 10 Objectives ......................................................................................................................................... 11 Limitations ........................................................................................................................................ 11 Presentation...................................................................................................................................... 12 Chapter 2 Literature Review ................................................................................................................. 14 Chapter 3 Comparison of Use of Lighting Simulation Software in Industry ......................................... 23 Introduction ...................................................................................................................................... 23 Survey methodology ......................................................................................................................... 23 Ethical Considerations....................................................................................................................... 25 Survey Results ................................................................................................................................... 26 Discussion.......................................................................................................................................... 37 Chapter 4 Comparison of Photometric Simulations ............................................................................. 42 Introduction ...................................................................................................................................... 42 Test Room ......................................................................................................................................... 42 Procedure.......................................................................................................................................... 48 Results ............................................................................................................................................... 49 Software Set-up ................................................................................................................................ 51 Running the Simulation..................................................................................................................... 52 Results ............................................................................................................................................... 56 Photometric Comparison .................................................................................................................. 57 External Horizontal Illuminance ........................................................................................................ 60 Discussion.......................................................................................................................................... 61 Limitations ........................................................................................................................................ 64 Chapter 5 Conclusions .......................................................................................................................... 66 Further Research............................................................................................................................... 69 References ............................................................................................................................................ 70 Bibliography .......................................................................................................................................... 72 Appendix 01 .......................................................................................................................................... 73 Survey Results ................................................................................................................................... 73 Appendix 02 .......................................................................................................................................... 82 5

Project Management ........................................................................................................................ 82 Original Project Proposal .............................................................................................................. 82 Management of the Project .............................................................................................................. 87

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List of Tables Table 1 Surface Reflectance Values ...................................................................................................... 43 Table 2 Test Room Measurement Values- Daylight Scene ................................................................... 49 Table 3 Test Room Measurement Values - Daylight and Artificial Light Scene .................................... 50 Table 4 Test Room Measurement Values - Artificial Light Scene ......................................................... 50 Table 5 - Unobstructed Horizontal Illuminance Test Results ................................................................ 61

List of Figures Figure 1 Survey Results - Question One, Respondents Location .......................................................... 27 Figure 2 Survey Results- Question Two, Respondents Profession........................................................ 28 Figure 3 Survey Results- Question 3, Previously Used Software .......................................................... 29 Figure 4 Survey Results - Question 4 .................................................................................................... 30 Figure 5 Survey Results - Question 4 - Filtered (Location) .................................................................... 30 Figure 6 Survey Results - Question 4 Filtered (Profession) ................................................................... 31 Figure 7 Survey Results - Question 5 .................................................................................................... 32 Figure 8 Survey Results - Question 5 Filtered (Location) ...................................................................... 33 Figure 9 Survey Results - Question 5 Filtered (Profession) ................................................................... 33 Figure 10 Survey Results - Question 6 .................................................................................................. 34 Figure 11 Survey Results - Question 7 .................................................................................................. 35 Figure 12 Survey Results - Question 7 Filtered (Profession) ................................................................. 35 Figure 13 Survey Results - Question 10 ................................................................................................ 36 Figure 14 Survey Results - Question 13 ................................................................................................ 36 Figure 15 Survey Results - Question 17 ................................................................................................ 37 Figure 16 AutoCad Image of Test Room ............................................................................................... 42 Figure 17 Photo of Test Room 12/04/14 .............................................................................................. 42 Figure 18 Photo of Test Room 12/04/14 .............................................................................................. 44 Figure 19 Photo of Test Room 12/04/14 .............................................................................................. 44 Figure 20 Photo of Measurement Apparatus 12/04/14 ....................................................................... 45 Figure 21 AutoCad Image of Measurement Grid .................................................................................. 45 Figure 22 Photo of Measurement Apparatus 12/04/14 ....................................................................... 46 Figure 23 Photo of Remote Measurement Display 12/04/14 .............................................................. 46 Figure 24 Dialux Calculation Window ................................................................................................... 53 Figure 25 Relux Calculation Manager Widow ....................................................................................... 54 Figure 26 AGI32 Daylight Study Parameters Window .......................................................................... 55 Figure 27 Ecotect Radiance Analysis Window 1of11 ............................................................................ 56 Figure 28 Daylight Only Simulation Comparison Graph ....................................................................... 57 Figure 29 Artificial and Daylight Simulation Comparison Graph .......................................................... 57 Figure 30 Artificial Light Simulation Comparison Graph ....................................................................... 57 Figure 31 Daylight Only Percentage Deviation Graph .......................................................................... 58 Figure 32 Artificial and Daylight Percentage Deviation Graph ............................................................. 59 Figure 33 Artificial Light Percentage Deviation Graph.......................................................................... 60

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Glossary of Terms

CASRO

Council of American Survey Research Organisations

CIE Sky Model

International Commission on Illumination has issued a range of ‘sky types’ which provide luminance distribution information which is used by lighting simulation software to calculate the likely light levels in simulated models during these ‘sky type’ conditions

Diffuse Reflection

The reflection of light from a surface which results in light being reflected at numerous angles as opposed to one angle as is the case with specular reflection

Ies File Format

File format for electronic transfer of photometric data created by the Illuminating Engineering Society of North America

Illuminance

Photometric measure of luminous flux incident on a surface per unit area (lx)

Lambertian Surface

An ideally diffuse surface which will result in light being reflected equally in all directions

Luminance

Photometric measure of luminous intensity per unit area (cd/m²)

Lux

Unit of Illuminance - See illuminance above

NATA

National Association of Testing Authorities Australia

Photometric Data

Information relating to the properties of light sources

Radiant Flux

Measure of total power of electromagnetic radiation (watt)

Radiosity

An algorithm used by lighting simulation software to predict lighting levels and produce realistic renderings based on dividing a scene into patches and assuming that all patches are ideally diffuse

Ray Tracing

An algorithm used by lighting simulation software to predict lighting levels and produce realistic renderings based on tracing theoretical light rays from light sources to observers (forward) and from observers to light sources (backward)

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Chapter 1 Introduction Introduction Lighting simulation software is now a widely used tool and an essential part of modern lighting design. These programs through the use of computers allow the complex and often massive quantities of calculations to be carried out within a reasonable timeframe.

Although, depending on the software being utilised, significant amounts of time can still be required to input all the relevant information into these models, this would be insignificant compared to the laborious task of attempting to carry out these calculations manually.

According to Augenbroe (2002) simulation is credited with speeding up the design process, increasing efficiency, and enabling the comparison of a broader range of design variants, leading to more optimal designs. Simulation provides a better understanding of the consequences of design decisions, which increase the effectiveness of the engineering design process.

This type of simulation software has been in widespread use for almost twenty years (Aries, Henson and Ochoa Morales, 2010), with numerous products being developed and improved. A survey in the use of such software tools in 2004 revealed that among the 342 respondents, 42 different lighting simulation software tools were used. (Fitz and Reinhart, 2004) A later survey examining daylight prediction methods identified 39 different lighting simulation software tools. (Galasiu and Reinhart, 2008)

Background to the Project My first introduction to lighting simulation software was as an engineering student, the lighting design of a fictional building was part of a project which my class was tasked to complete. We were given a brief overview of Dialux, a lighting design simulation program developed by Dial, to facilitate the work required. I was immediately impressed with the apparent sophistication of the software, the ease at which it calculated my basic design 9

and produced impressive images on screen representing a visualisation of my work; furthermore it was free to download.

Many years later as I was working as a design engineer in electrical services, the need to carry out lighting calculations for both simple and complex scenes once again required the use of such software. As my early experience was with Dialux, I chose to use this product not really considering any others. A Canadian colleague preferred Relux for his designs, software I had not previously heard of. He confirmed that he found it easier to use than Dialux for simple calculations of lighting levels in single rooms or open plan floors whereas my English colleague used mainly AGI32. The three different simulation tools used by three different engineers to do essentially the same work interested me and I began to wonder if there is any one which is better than the others or is it just down to personal preference.

The following study will compare four different simulation tools widely used in industry and will examine who, where and why they are used. A further technical comparison will evaluate how close they each get to actual measured levels in a test environment and explore the reasons for this.

Selection of Software for this study Three of the simulation software tools selected for the following study have been chosen based firstly on personal experience of which appear to be most widely used in the engineering industry and secondly on feedback from users in the lighting design industry.

These are Dialux, Relux and AGI32. Further research into the subject highlighted that a fourth program, Radiance, is frequently cited and suggested to be amongst the most accurate available. It is for this reason that this program was added to the comparison study. However, Radiance lacks a user interface and therefore requires a significant programming aptitude. In order to overcome a potentially time consuming process in simulating with Radiance, a third party program Ecotect 5.5 will be used to model the 10

geometry of the scene in the simulation comparison section. The final model can then be exported to Radiance for simulation purposes.

Objectives The objective of this project is to: •

Identify which software packages are most popular amongst professionals working in lighting design and identify the reasons for this

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To examine the calculation methods utilised by each of the four simulation software packages

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To simulate a range of identical scenes in each of the programs and observe any difference in results

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To analyse why this may have occurred

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To compare the above results with measured values utilising testing equipment in a test room

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To analyse why this may have occurred

By achieving the above specific objectives of the research it is hoped that sufficient information is provided to allow readers to better understand the subject of lighting simulation software. Developers of such products may gain useful insight from the results of the questionnaire which will highlight user’s issues, preferences and experience levels.

In addition, users may gain insight into the extent of variations in simulated results which can occur across a number of programs and offer some awareness of the factors that can cause these differences.

Limitations The research documented below has been conducted with the following limitations: •

The research only provides a basic understanding of the calculation methods used by lighting simulation software and does not describe in detail the mathematics utilised 11

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The research only examines the calculation methods utilised in the four programs being investigated and does not provide information on other calculation methods or algorithms used by other software tools. (Photon Mapping)

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Only three possible light scenes are simulated as part of the photometric comparison.

Many alternative types and combinations could be simulated to explore how the programs handle changes in various parameters.

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Only clear sky conditions are simulated as this was considered appropriate to the sky conditions of the test day. However, an overcast sky comparison would provide further useful information on the programs simulation ability and possibly highlight further differences between them.

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Only internal horizontal calculation points are measured and simulated. External horizontal illuminance values are not recorded on the test day. Some external horizontal illuminance simulation is carried out subsequently for further consideration.

Presentation The following study has been presented in five chapters. Chapter one provides the introduction which includes the background to the project, the selection of the software, the objectives and some research limitations.

Chapter two outlines the literature review which describes the most commonly used algorithms in lighting simulation software as well as other relevant studies and surveys concerned with the use and accuracy of lighting simulation tools. These are presented for the most part under the headings of the four programs being examined as part of this study and are followed by a brief conclusion.

Chapter three sets out the methodology and results from an online survey which gathered information on the use of lighting simulation tools worldwide by professionals. The analysis

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of this survey is followed by a detailed discussion which endeavours to provide the required insight as set out in the objectives.

Chapter four provides the methodology and results from the simulation comparison. The measured photometric values from the test room are documented and compared to the results produced by each of the software programs. A discussion is provided relating to the outcomes of the process.

Chapter 5 provides a conclusion to the research and lists some further work which could be undertaken to address some of the shortfalls of this study

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Chapter 2 Literature Review Introduction There are a significant number of software programs available for use in lighting simulation. This suggests that it is indeed a valuable design aid currently being used by many professionals.

A survey carried out at the turn of the century confirmed this view stating that 70% of firms use such tools to enhance their designs and 58% felt that it speeded up their design process and provided confidence in their design. (Feriadi, Hien and Poh 2000) Although the accuracy of such software tools will be discussed later in this paper, a recent survey carried out in 2008, highlighted that out of all participants less than 1% expressed any concern over the accuracy of such programs (Galasiu and Reinhart, 2008), indicating that the industry has confidence in the results provided by simulation tools.

Although there are a significant number of different products available, most of these software packages rely on only two basic approaches to computing the distribution of light in a scene, Ray Tracing and Radiosity. (Roy, 2000)

Calculation Methods

Ray Tracing was first developed by Whitted in 1979 as a technique primarily used in image generation. The technique involves tracing the path of a light ray from a source to the eye where the image is formed, this is called forward ray tracing. As many of the light rays leaving the source never reach the eye and therefore do not contribute to the image, this method can be wasteful on computational resources. The method of backward ray tracing introduced in 1986 by Arvo, whereby the path of light is traced from the eye back to the source is now more commonly used in software. (Herbal and Kota, 2009)

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Ashdown defines Radiosity as ‘a finite method that simulates the transfer of radiant flux between Lambertian surfaces’ (Ashdown, 2001). This is achieved by dividing each surface in the scene into a mesh of elements called patches. This method assumes each surface to be ideally diffuse (Lambertian), therefore having constant radiance independent of viewing direction. This is fundamentally different to the Ray Tracing method which is dependent on viewing direction. Radiosity calculates the light leaving all light sources, which surfaces it reflects from and so on until all the light has been absorbed by all the surfaces within the scene.

Each method has advantages over the other; however there is little consensus on which is better suited to lighting simulation. Roy states that ‘Ray Tracing is probably the best choice to generate photo-realistic images where subtleties of specular reflections and refractions can be handled quite well. On the other hand Radiosity is better for handling diffuse reflections and shadows’. (Roy, 2000) Although in agreement on the ability of each algorithm, Altman and Apien-Bennewitz are of the opinion that Ray Tracing is better suited to lighting simulation, stating that ‘the algorithms of ray-tracing are superior to those of radiosity, as they calculate the light transport for surfaces which are not ideally diffusely reflective. If redirection of daylight or indirect lighting via the ceiling is considered, with real ceiling materials which usually deviate from an ideal Lambertian light-scattering characteristic, the radiosity solution is inadequate’ (Altman and Apien-Bennewitz, 2001).

Radiance

The following review of the literature will highlight that the vast majority of previous studies into lighting simulation have incorporated the Radiance calculation engine developed by the Berkley Institute California. (Campbell et al, 1999) During a 2008 survey into the use of daylight prediction methods, Reinhart and Galasiu found that over 62% of

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programs used were partly or exclusively based on the Radiance backward ray tracer.

(Galasiu and Reinhart, 2008) Radiance is a Ray Tracing programme which has received several validations. Li and Tsang concluded that Radiance could simulate with reasonable accuracy day lighting on a corridor in their comparison with measured data in an experiment in 2004. (Li, Tsang, 2005) In addition, Ng, Wei, Poh and Nagakura also demonstrated that Radiance is reasonably accurate in simulating the light environment of a museum in the tropics. (Nagakura et al, 2001). Christakou and Amorim found that Radiance has a high potential for evaluation of daylight in architectural projects. (Amorim and Christakou, 2005) Radiance is open source and free to download, but as mentioned above, lacks a user interface of its own. It is for this reason that Ecotect 5.5 will be used to model the scene in this study prior to exporting to Radiance. A similar approach was used by Stravoravdis while studying the possibility of retrofitting office lighting with LED solutions. He compared the same four lighting simulation packages as will be addressed here, in order to select the most accurate for his project. A test room was set up and modelled in each software package, calculation points were taken and compared. Although all programs produced fairly similar results, Radiance performed ahead of the others. (Stravoravdis, 2013) However, this study was only concerned with artificial light and did not have a daylight component. Daylight simulations are generally more challenging in terms of modelling accuracy and parameter settings than artificial light calculations. (Relux, 2010) Relux Relux is a free to download lighting simulation package which is primarily used for artificial lighting applications. It is most popular in European markets. (Ochoa, Aries and Hensen, 2012) It utilises both Raytracing and Radiosity calculation methods and allows the user to

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select between them. The Raytracing method is an enhanced version of the Radiance program. (Relux 2010) It is the standard Radiosity method which will be utilised in this particular comparison study.

Although in agreement with the above authors on Radiance's accuracy, Christakou and Silva concluded that Relux was the most adequate for use by architects for daylight simulation when considering criteria such as Modelling, User interface, Output, Processing Efficiency, Validation and Support. Their study compared two different packages, Relux and Ecotect (as Radiance interface), although the comparison did not extend to a real test room and therefore it is unclear how they arrived at their calculation of accuracy. (Christakou and Silva, 2004) A later study by the same author compared Desktop Radiance, Rayfront, Relux and Lightscape and confirmed his earlier conclusion that Relux is the most adequate software for architectural design when predicting daylight. (Amorim and Christakou, 2005)

Dialux

Dialux which is developed by Dial GmbH in Germany is also available free to download.

Similarly to Relux, it is primarily used for artificial lighting design, although again has the ability to consider daylight. Dialux utilises a radiosity algorithm for its calculations. The current release of Dialux is still only capable of modelling a fairly basic range of objects and textures; however Dial has released a product called Dialux Evo which boasts more accurate calculations and has extensive libraries of textures, shapes and furniture. Dialux Evo does not have the ability to simulate daylight and therefore was not considered suitable for this comparison study. The literature has revealed that although widely known and available, very few studies in the context of photometric validation have considered Dialux with the exception of Acosta, Navarro and Sendra’s ‘Toward an analysis of

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daylighting simulation software’ (2011) and 'Daylight Calculations in Practice' (Christoffersen, et al 2013) both of which will be discussed below.

AGI32

AGI32 is a lighting simulation tool which in contrast to the others is only available on the purchase of a licence. It is developed by Lighting Analysts and is most prevalent in North America. It is used for both artificial and daylight lighting simulations. It utilises a Radiosity algorithm for its lighting calculations. Similarly to Dialux, AGI32 seldom features in the available literature with regard to previous studies.

One exception is the study by Kensek and Suk, while examining lighting simulation software in the context of daylight prediction compared three different programs, AGI32, Ecotect and 3D Max Design. This study found that using different simulation software programs gives different simulation results; they found that AGI32 calculated the highest results and 3Ds Max the lowest in all test cases, although these were not compared to an actual test room where real measurements were taken. (Kensek and Suk, 2011) Previous Comparison Studies Although there are few studies which have examined and compared the particular group of software packages which have been selected to form the basis of this study, there have been a significant number of previous comparison studies which have focused on one or more of the programs in question.

On reviewing these previous comparison studies it became evident that a significant number of them were primarily concerned with the evaluation of daylight within interior spaces. Amongst these were Acosta, Navarro and Sendra’s ‘Toward an analysis of daylighting simulation software’ (2011). Their study compares Lightscape, Desktop Radiance, Lumen Micro, Ecotect and Dialux against the measurements taken from a 18

miniature model test room with artificial sky machine. They found that the different software tools produced significantly different results; they attribute this to the programs using different interpretations of the sky model. (Acosta, Navarro and Sendra, 2011) A recent study commissioned by the Danish Building Research Institute focused on evaluating the ability of a range of programs to accurately calculate daylight factor in various room types. Nine programs were selected, including the programs selected for this study with the exception of AGI32. The study concluded that most of the programs were capable of calculating daylight factor in most room types with some exceptions, one such being that Relux utilising Radiosity could not simulate a room with borrowed light.

(Window and Skylight) The study also provided some conclusions regarding the user friendliness of the programs. Velux Daylight Visualiser scored ahead of all others within this criterion, however the objectiveness of these findings should be considered as two of the study's authors are Velux employees. (Christoffersen, et al 2013) Roy's comparative study examined not only the accuracy of the lighting simulation programs but also endeavoured to provide some insight into the usability of them. His attempt to utilise a survey to gather some information in this regard proved unsuccessful due to a poor response rate, although some of this is probably due to the very few questionnaires issued. Roy opted to review other comparison experiments and provides a gathering of information as opposed to any of his own testing. Although unable to identify a 'best program', he concludes that Radiance seems to outperform most others in accuracy when compared to scale models and test environments. (Roy, 2000) A report produced in 2001 by Altmann and Apian-Bennewitz has taken the approach that the only way to really compare lighting simulation programs is to use a complex building with numerous objects and comprising of natural and artificial light sources. Three programs were selected to model one of the vaults of the Kimbal Art Museum, 19

3D_StudioMax, Lightscape and Radiance. They conclude that the Radiance program is far superior when considering a complex scene, as the Ray Tracing algorithm considers non diffuse reflectance. (Altmann and Apian-Bennewitz, 2001) Reinhart has written numerous papers on daylight simulation software and its accuracy, many of which incorporate the use of Radiance. Reinhart and Walkenhorst's validation of Radiance based daylight simulations for a test office with blinds found that daylight factor could be accurately calculated within a few percentage points using the program Dayism.

(Reinhart and Walkenhorst, 2001). In an interesting study Reinhart has also investigated how accurate the results obtained by novices from lighting software can expect to be. This study comprised of 69 architectural students who were all asked to model a university lecture room and carry out a daylighting simulation using either Radiance or Ecotect. The study highlighted that all students preferred to use the Ecotect product due to the complexities of Radiance, but demonstrated several major shortcomings in their ability to model the environment correctly. It also showed that Ecotect reported on average a 36% lower result compared with Radiance. (Ibarra and Reinhart, 2009) A follow up study in 2012, explored the use of a ‘teaching toolkit’ designed to reduce the mistakes commonly made and highlighted in the previous study. This work concluded that the use of such a tool kit of exercises was highly successful, quoting an increase of 24% in ability to predict daylight factors. (Ibarra and Reinhart, 2013) Previous Surveys

There have been several surveys carried out over the last decade relating specifically to lighting simulation software and again most of which were concerned with its application with respect to daylighting prediction. Of these Reinhart and Fitz’s survey in 2004 provided some interesting findings as well as providing a significant review of previous surveys in the

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preceding decade. They concluded that many users of such software still find its use difficult to master although its use in general has significantly increased amongst design professionals in recent years. (Fitz and Reinhart, 2004)

A subsequent survey by Reinhart and Galasiu in 2008, focusing more generally on daylight design practices found that time constraints was one of the biggest obstacles to using lighting simulation software tools. (Galasiu and Reinhart, 2008)

Conclusion The review of the literature has shown that a vast number of lighting simulation programs are available. The undertaking of a single study to compare and examine all the programs would prove too laborious a task. At best, one can only attempt to compare a select number of programs, as has been the case for the existing studies described above.

Furthermore, the scope of any comparison study must be further specified, criteria such as ability to simulate daylight, to simulate artificial light both reflected and direct, simulation in different sized rooms, with multiple openings, usability of software, modelling capability, rendering results, speed etc. could all be examined in much detail across a range of programs, thus a complete analysis of available programs is unlikely to occur due to the magnitude of the task of encompassing all the parameters above in any one study. It is for this reason that Ochoa, Aries and Hensen decided to take the approach of mapping out the developments of lighting simulation software. Their report provides a comprehensive literature review which not only details the history of lighting simulation software but also touches on numerous available programs and a significant volume of previous works by others in the field. (Aries, Hensen and Ochoa, 2012) In contrast to the existing research, the following study hopes to provide a comparison of four of the most widely used lighting simulation programs available. The comparison will

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not just touch on the ability of the programs to model and simulate in a select range of scenes but will first validate that these program are amongst the most popular in industry today and will investigate a number of factors surrounding their use.

On conclusion of this initial research, the programs will then be examined in the context of photometric comparison whereby each of the programs will be tasked with modelling and simulating a simple room scene incorporating both natural and reflected artificial light. The purpose of this testing is not to validate the programs accuracy but to highlight any significant difference between the results produced by them and that compared to the measured values.

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Chapter 3 Comparison of Use of Lighting Simulation Software in Industry Introduction Lighting simulation software is widely available across the world and used by many different professional groups in their daily work. A considerable number of programs are currently on the market as highlighted during the literature review. Professionals concerned with predicting the lighting effects of both artificial and daylight sources have considerable choice when selecting an appropriate software tool to utilise. This research is concerned particularly with the use of four such tools, Dialux, Relux, AGI32 and Radiance.

The following section details the results of a survey conducted which attempted to gather some insight into which of the above software programs are most commonly used for lighting simulation and why.

Survey methodology The questionnaire was designed to gather information on the use of lighting simulation software in industry today. Questions were selected to focus on the participant’s background, the type of work being carried out, their geographical location, the frequency of use and the reasons why one tool was used over another.

It was important to make the questionnaire as straight forward as possible and not to have too many questions if a high dropout rate was to be avoided. In total 18 questions were drafted to gain the required information for the analysis. All questions provided a multiple choice answer with the ability to either choose just one answer or all relevant answers depending on question type. Many questions provided an “other” option whereby respondents could provide additional information as required.

Once the questions were selected, the final survey was uploaded onto an online survey service “Question Pro”. Question Pro was selected out of a possible three similar services.

“Survey Monkey” and “FreeOnlineSurveys.com” were also considered. The original criteria 23

for selection of a suitable site were based on cost, analysis options, question options and ease of inputting questions. It was found that the discounted sites had several limitations when trialled which included: •

Limitation on the number of questions allowed

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Time consuming and tedious to input questions

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Limitations on analysis options

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Minimum contract durations for paid premium services

Although it was required to upgrade to a premium account with Question Pro in order to provide the increased functionality required to carry out the survey as intended, the costs associated with this option were only applicable during the survey phase with no minimum contract duration.

The survey was made available between the 6/1/2014 and was concluded on the 12/3/2014. During this time links to the survey were advertised on the following LinkedIn Discussion Groups and professionals who had used such software for their work were encouraged to take part.

• Lighting Simulation • Australian Building Services (M&E) • Building Services and Environmental Design • Building Services Design Consultants (UK) • Building Services Engineers • Chartered Institute of Building Services Engineers • Electrical Design and Drafting – Building Services • Electrical Engineering • Electrical Design Engineers • Electrical Design Engineers -Power System and Lighting 24

• Engineers Ireland In addition to the above, the questionnaire was circulated through personal contacts made within the industry.

Ethical Considerations According to the CASRO, (Council of American Survey Research Organisations) the four fundamental ethical principles in conducting research are that respondents should be willing participants, appropriately informed about the surveys intentions and how their personal information will be used and protected, sufficiently satisfied with their survey experience and willing to participate again in survey research. (CASRO, 2011) In an age where much of our daily business is done with the use of the internet, the ability to elicit information from persons without their knowledge has never been easier.

Computer spyware can be downloaded onto someone's personal computer without their express permission and can be used to gather information on their internet usage, which in today's world can obtain details on anything from their taste in music to their shopping habits. The use of such practices has no place in ethical research and should always be discouraged.

Using information in a way that is contrary to how it was to be used as communicated to the participants can also be common practice. Research may be used as a guise for sales or solicitation.

Divulging personal information about the participant should not occur without the express permission of the participant. Such information can be a valuable commodity and organisations can be keen to get hold of data relating to certain groups which can assist in their direct marketing of products. Such activities are commonly an annoyance to most people and very few would be keen to have their details used in this way.

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Lengthy interviews, sensitive subject matter, intimidating or uncomfortable environments should all be avoided to ensure the survey experience remains positive.

The survey utilised for the purposes of this study ensured that all respondents were willing participants by requesting them to actively follow the required web link to the survey site.

Furthermore the reasons for the survey were outlined both in the initial invitation and again on the opening page of the survey itself. It was detailed what kind of insight the survey wished to gain and also that the purpose of the wider study was for the partial fulfilment of a Master’s Degree.

As the survey did not require any respondent to provide identifiable information, it was not required to inform the participants how this personal information would be used.

In order to try and ensure that the respondents were satisfied with their survey experience, the number of questions was kept below twenty and each question provided a multiple choice answer to ensure ease in providing the information. I also provided estimated time for completion in the introduction to the survey and updated this to reflect the actual average time that respondents were taking to complete the survey. It was thought that accurately informing the participants of the time commitment required would add positively to their survey experience.

Although difficult to ascertain, without actually including it as a final question, I would hope that the participants would take part in similar research should it be undertaken.

Survey Results 182 respondents from 45 countries around the world took part in the questionnaire, although only 129 of those respondents completed it fully. The following data is based on the answers from those 129 respondents. Although a total of 18 questions formed the questionnaire and provide interesting data, only 10 have been detailed below for the

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purposes of analysis. These have been deemed pertinent to understanding why certain software is used over another. However data from all questions has been used for the purposes of the discussion and conclusion at the end of this section and subsequent sections. In addition all questions and their associated responses can be viewed in Appendix 01 Question 1 – Respondents Location Participants were asked to select a location which best described the place where they worked. The following chart illustrates their responses.

Work Location North America 17%

22%

1%

South America Europe

1%

Middle East

6%

Asia

8%

45%

Africa Australia

Figure 1 Survey Results - Question One

For the purposes of further analysis, the above information was grouped into the following four locations: •

Africa/Asia/Middle East

15%

•

America (North and South)

18%

•

Europe

45%

•

Australia

22%

27

Question 2 – Respondents Profession Participants were asked which best described their profession. The following chart illustrates their responses.

Profession

Electrical Engineer Lighting Designer

6% 3%

6%

6%

Architect 37%

Interior Designer Energy Consultant

0% 8%

Software Developer

3%

Academic 31%

Lighting Product Sales Rep Other

Figure 2 Survey Result- Question Two

Similarly to above, this information was also grouped into the following categories for the purposes of further analysis.

•

Engineers (Electrical Engineers/Energy Consultants)

45%

•

Designers (Lighting Designers/Interior Designers/Architects)

34%

•

Researchers (Academic/Software Developer)

9%

•

Other (Other/Lighting Product Sales Reps)

12%

Question 3 – Simulation Software Previously Used Participants were asked which Lighting Simulation Software tools they had previously used.

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% of Total Respondents

Lighting Simulation Software Previously Used 100 80 60 40 20 0 Dialux

Relux

Radiance Radiance 3rd party

AGI32

Other

Figure 3 Survey Results - Question 3

Across all groups Dialux was the most widely used with 77% of all participants having tried this software followed by Relux at over 44%. Just over 19% of those surveyed had used Radiance or Radiance through another program, with over 33% having used AGI32. 28% had used other lighting software tools not listed which comprised of a total of 27 different software tools.

The above results highlight that Dialux is certainly widely known and tried amongst lighting design professionals.

Question 4 – Simulation Software Not Previously Heard Off In contrast to the previous question participants were asked which of the software tools they had not previously heard off.

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Lighting Simulation Software Not Previously Aware Of 2% 4% Dialux 23% 50%

Relux Radiance AGI32

21% Heard of them all

Figure 4 Survey Results - Question 4

In line with the results of the previous question Dialux was the best known product with only a mere 2% not having heard of this software before, again closely followed by Relux at only 4% while over 50% of all respondents had heard of them all.

In order to be able to identify if geography or profession had any significant influence in the results above, the results were further analysed based on these two categories. The following charts detail the results when filtered.

Lighting Simulation Software Not Previously Aware Of 60 50 40 30 20 10 0

Dialux Relux Radiance AGI32 Heard of them all

Figure 5 Survey Results - Question 4 - Filtered (Location)

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Although Dialux is known throughout all regions, it is Relux’s presence in the European market that has influenced the figures in the first chart as 45% of all respondents identified being from Europe. The above chart also highlights that significant numbers of professionals in Europe and Asia/Africa/Middle East have never heard of AGI32.

Respondents in America and Australia are much less likely to have heard of Radiance compared with that of the other two locations.

Clearly geographical location influences which software tools one is likely to be familiar with and therefore try.

Lighting Simulation Software Not Previoulsy Aware Of 100 80

Dialux

60

Relux

40

Radiance AGI32

20

Heard of them all

0 Engineers

Designers

Researcher

Figure 6 Survey Results - Question 4 Filtered (Profession)

When considering the results amongst the profession sub-categories, it is worth noting that engineers were more likely not to have heard of AGI32 and Radiance. The designers group in contrast had over 60% aware of them all, while Radiance being the least known tool. The researcher’s group identified that over 90% of its group was familiar with all software tools presented.

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Question 5 – Simulation Software of Choice Participants were asked which of the lighting simulation software tools they preferred to use.

Lighting Simulation Software of Choice Dialux 16%

Relux 40%

Radiance

18% Radiance 3rd party

5%

7%

AGI32 14% Other

Figure 7 Survey Results - Question 5

40% of respondents selected Dialux as their software of choice, followed by AGI32 at 18%, Relux at 14%, with only 7% and 5% for Radiance and Radiance through another program respectively. 16% of respondents selected another software tool not listed. These consisted of only 8 different lighting simulation software products.

When applying the filters of location, the results dramatically change, highlighting that AGI32 and other tools not listed make up almost 80% of preferred lighting simulation software used in America, whereas in Europe, Dialux and Relux are by far the most popular. Africa/Middle East and Asia favour Dialux over any others and contrastingly in Australia, Dialux and AGI32 are approximately the same at 46% and 43% respectively.

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Lighting Simulation Software of Choice 70 60 50 40 30 20 10 0

Dialux Relux Radiance Radiance 3rd party AGI32 Other

Figure 8 Survey Results - Question 5 Filtered (Location)

If profession is used as the basis of comparison, Dialux is found to be the most popular amongst engineers. However, on examining the other two professional groups its popularity wanes somewhat and the preferences become more even as can be seen below.

Lighting Simulation Software of Choice 60 50

Dialux

40

Relux

30

Radiance

20

Radiance 3rd party

10

AGI32 Other

0 Engineers

Designers

Researcher

Figure 9 Survey Results - Question 5 Filtered (Profession)

The software tools which were highlighted as being amongst respondents tools of choice but which were not on the list provided include the following: •

Calculux

•

Lightscape 3.2

•

Litestar

•

Visual

•

3D Max Design

•

Elum Tools

•

Optiwin 3D Pro

•

Daylight Analyisis

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Question 6 – How long have you been using Lighting Simulation Software Participants were asked how long they have been using lighting simulation software.

Several time categories were provided with 5 year intervals. Over 40% selected between 5 and 10 years with approximately equal numbers at 20% each selecting 0 to 5 years and 10 to 15 years.

Lenght of Time Using Lighting Simulation Software

9%

5% 25%

Less than 5 Years Between 5 - 10

20% Between 10 - 15 41%

Between 15 - 20 Longer than 20

Figure 10 Survey Results - Question 6

Question 7 – Reasons why software is selected Participants were asked why they choose to use the software tool that they selected above. Several multiple choice answers were provided with the option of selecting ‘other’ and giving an answer not provided. Only 11% selected an answer not provided. The most selected answer was that they had tried more than one program and felt that their program of choice was the most suited to their work. This accounted for 29% of all respondents’ answers. Interestingly 15% of respondents selected that it was the first tool that they had used and had therefore stuck with it.

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Reasons for Using Preferred Software Tool It’s the 1st software I used 11%

I tried more than 1 but feel this is more suited to my work I tried more than 1 but feel this one is the best I hav researched several and have selected this one It is free to download

15%

9% 8% 29% 15%

It is the quickest for the projects I moslty use it for Other

13%

Figure 11 Survey Results - Question 7

When examining the different professional groups, engineers were more likely to have tried a number of programs and stuck with one or just stuck with the first program used. In contrast Researchers and Designers were much more likely to have researched several programs and select their program of choice from this process.

Reasons for Using Preferred Software Tool 40 It’s the 1st software I used 35 I tried more than 1 but feel this is more suited to work

30 25

I tried more than 1 but feel this one is the best

20

I hav researched several and have selected this one

15

It is free to download 10 It is the quickest for the projects I moslty use it for

5 0

Other Engineers

Designers

Researcher

Figure 12 Survey Results - Question 7 Filtered (Profession)

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Question 10 How Often do you use Lighting Simulation Software Participants were asked how often they use lighting simulation software.

Frequency of Use of Lighting Simulation Software 9% Almost every day 17%

42% Once a week Once a month 32% 2-6 time a year

Figure 13 Survey Results - Question 10

Question 13 – What Prevents you from Using the Software More Often Participants were asked to provide reasons if any for not using lighting simulation software more often. The vast majority (59%) identified that they were able to use the software as often as was required, while 16% found that time constraints hindered more frequent use.

These results were fairly typical across all filters.

Obstacles to More Frequent Use of Software 3%

Lack of Training

2% 6%

Too Complex Time Constraints

16%

Client does not pay for it 10% Cost of Software

59% 4%

N/A I use it as often as required Other

Figure 14 Survey Results - Question 13

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Question 17 – How accurate do you believe the results of simulation software to be Participants were asked how accurate they believed the results of the lighting simulation software to be assuming that all the information had been inputted correctly. By far most respondents selected between 80 and 100% with the highest concentration being between 80 and 90% at 44% of total responses.

How Accurate Do You Believe Lighting Simulation Software To Be 2% 2% 20-40% 17%

10%

40-60% 60-80% 80-90%

25% 44%

90-95% 95-100%

Figure 15 Survey Results - Question 17

Discussion The above results indicate that the use of a specific lighting design simulation package has a positive correlation with geographical location. One is more likely to have heard of and tried Dialux and Relux if from Europe. Dialux and Relux were both developed in Europe and have a strong connection with many of the lighting manufacturers which supply downloadable plug-ins for Dialux and Relux software which facilitates the importing of photometric data and may speed up the simulation process. As time constraints was highlighted as being the biggest obstacle to using software of this type where obstacles existed, perhaps this type of support and compatibility from lighting manufacturers encourages the use of these particular products over others.

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Unlike Dialux though, as soon as one leaves Europe, the popularity of Relux wanes considerably with less than 5% of respondents outside of Europe selecting it as a tool of choice. Dialux enjoys widespread use in all but one location, that being the Americas.

However, just examining the results above without deeper investigation might give a false impression of which program is most popular. For instance, the returned questionnaires which highlighted Dialux as being the software tool of choice, show that amongst these participants only 18% had used AGI32, in fact many had not even heard of it. Compare this to the users who identified AGI32 as their tool of choice, over 70% had used Dialux. This may lead one to conclude that given the choice of one over the other, AGI32 is the preferred choice even if overall numbers are lower. The Dialux users have in the most part only ever used Dialux and Relux. In reality, one can only conclude that Dialux is only preferred over Relux, and not the other tools listed.

Arguably the only true way to determine which of the software tools is preferred is to compare respondents who reported having used all of them, unfortunately this only equates to 3% of the total, a mere 4 questionnaires and could not be considered a wide enough sample. Be that as it may, two out of those four selected AGI32, one selected Relux and the last did not give a tool of choice only responding that is was dependant on the scene being simulated.

Accepting that the choice of software tool is dependent on the selection of other tools one has been exposed to, the results can be further analysed on that basis. As mentioned, Dialux users for the most part are only choosing to use Dialux over Relux or because they have only ever used Dialux. Over 38% of Dialux users have only used Dialux and a further 26% have only used Dialux and Relux. Out of the respondents who reported only having used Dialux, over 55% gave the reason as being that it is the first software tool that they had used and had never tried any others. It is also worth noting, that over 83% of Dialux 38

users reported that they have only been using this type of software for less than 10 years and only 49% identified their level of proficiency as advanced with 43% as medium.

Examining the responses from the users of AGI32 in a similar fashion indicates some obvious contrasts, only 21% of AGI32 users have only used AGI32, with over 52% having used at least three of the software tools listed and as previously highlighted over 70% of these were Dialux. The reasons selected amongst AGI32 users for why they choose to use it over others are ‘having researched several and selecting it’ at 26% and ‘tried more than one and believe it is best’ at 26%, with the remaining reasons split across the other options. It would certainly appear that users of AGI32 tend to have used a wider selection of lighting simulation tools and selected it by choice; this is despite it being the only software tool which is not free to download. (With the exception of some radiance based 3rd party programs) Another contrasting point is that only 50% of AGI32 users have been using lighting simulation software for less than 10 years, suggesting a more experienced user base. Over 70% of users described their proficiency level as being advanced, with just 26% as medium.

Considering respondents who selected Relux as their tool of choice, only 7% had only used Relux. Over 53% had only used Relux and Dialux previously, and over 47% had used at least three of the tools listed (usually Dialux, Relux and Radiance), with the most popular reasons for using Relux cited as being a result of researching several and selecting Relux.

The high proportion of Relux users having used Radiance may be contributed to the fact that Relux utilises a Radiance based calculation engine, therefore Relux users may be more likely to be exposed to Radiance and experiment with the actual Radiance software which is also free to download. Relux users had similar experience levels as Dialux with just 59% describing their proficiency as Advanced and 35% as Medium.

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Although only 7% of total respondents selected Radiance as their tool of choice, which equates to 9 questionnaires, I believe it is still worth analysing these further. Interestingly, over 66% of these users are from Europe, with only 11% (single user) from North America, which is surprising considering this software has been developed by the University of California. Only a single user reported having only used this tool, whereas most had used several, mainly consisting of a combination of Relux and Dialux. Only one reported having used AGI32 before, again this may be explained due to geography, as that user was from North America consistent with previous analysis. Similar to AGI32 only 55% of users of Radiance have been using this type of software for less than 10 years. 100% of users described their proficiency as advanced which would have been expected as this software differs from all others by the fact that it does not have a user interface and requires the user to have a sound programming knowledge.

It is for the above reasons that many choose to use this software through 3rd party software. A further 6 questionnaires were completed by such people, and again similarly to the suers of Radiance itself, users of these software tools have highlighted that all but one had used several other tools and selected this one out of choice. However, in contrast, over 83% have only been using lighting simulation software for less than 10 years, with over 80% describing their proficiency as advanced.

In summary, Dialux is an internationally widely used lighting simulation tool, but a significant number of users would be among the less experienced and less proficient users of lighting simulation software. It is primarily used by professionals who have only had experience with it or Relux and most of these would be amongst the engineering profession.

AGI32 is less known and is only in widespread use amongst professionals in America and Australia, however it appears to be a preferred tool of choice by many who have used and 40

researched several others. Its users are more advanced and have more experience than the users of Dialux and Relux with a significant number being lighting designers.

Relux is primarily used in Europe, with many of its users sharing the experience levels of its Dialux counterparts; it is far less likely to be selected over Dialux and is used equally between all user groups.

Radiance is the least known of all the software programs selected and is primarily used by researchers. Its users are of advanced levels who have selected the use of this program after researching and using several others.

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Chapter 4 Comparison of Photometric Simulations Introduction The following section of this research will document a comparison of photometric results for a series of scenarios simulated in Dialux, Relux, AGI32 and Radiance (through Ecotect).

The scenarios will include a daylight only scene, daylight and reflected artificial light scene and a reflected artificial only light scene. Each scene will be constructed in a real test room where actual photometric results will be recorded. Each simulation package will then have the required parameters inputted and simulations run. The simulated results will be compared to that of the actual results to highlight the extent of the differences between these values.

Test Room Dimensions The test room was a small room with one window and one door. The room measured 3600mm Long x 3060mm Wide x 3300mm High. The window measured 810mm Wide x 1460mm High and the door measured 810mm Wide x 2100 High.

Figure 16 AutoCAD Image of Test Room

Figure 17 Photo of Test Room 12/04/14

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Reflectance Measurements In order to accurately model the test room in the lighting simulation software is was vital to measure the reflectance of all surfaces within the room. Originally it had been planned to use luminance and illuminance meters to determine the reflectance of the internal surfaces using the formula ρ = L x π / E. (SLL, 2001) However due to difficulties in obtaining a luminance meter; it was decided to try an alternative method. A sample reflectance card is provided as part of the CIBSE Lighting Guide, section 11. The card has 48 colour patches each with a hole; the concept is to place the card over the surface to be checked and to identify the colour and shade closest to the sample. This corresponds to a reflectance value which is claimed to be “to the degree of accuracy appropriate for use in lighting design software calculation routines”. (SLL, 2001) This procedure was carried out for all surfaces in the test room and these values were noted. The below is a summary of the values of reflectance recorded and subsequently used for modelling in each software program.

Surface Floor Ceiling Walls Light Screen Box Door Window Blinds

Chart Value A1 A6 H5 C4 C4 H6 H6

Reflectance 10 74 72 48 48 81 81

Table 1 Surface Reflectance Values

Transparency of Window The transparency was assumed to be at 81% based on typical values for single glazed panes. The glass was cleaned on both sides prior to testing.

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Artificial Light Source The luminaire which was selected to provide the artificial light source for the modelling was a Tantec 18W LED down light. The luminaire was provided for the study by E-Lumen 8.

The type of light source was not overly important, once accurate photometric data in the form of ies files could be obtained. Ies files have been a standard file format for the electronic transfer of photometric data and are widely used by lighting manufacturers.

There are other file formats available and some software can interpret several formats, however the ies format is the only format which could be interpreted by all the software programs being tested and therefore was selected as the standard for this comparison study.

Obstacles to Overcome As the test room contained a stainless steel chandelier type light fitting which could not be disconnected and was too complex in its geometry to accurately model, it was decided to use a cover which could be modelled to block it. A 500mm x 500mm card was used and fixed to the underside of the light fitting. Similar card was also used to box in a small table to provide the platform the test luminaire would sit on during testing. This allowed for a simple geometric shape of known colour and size to be modelled.

Figure 18 Photo of Test Room 12/04/14

Figure 19 Photo of Test Room 12/04/14

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The decision to sit the test luminaire on this box and shine upwards was taken firstly out of ease, as to try and suspend the fitting from a height would have proved problematic, but also it provided for a level of complexity, as the calculation grid would be recording the reflected light from the ceiling and walls and no direct light from the test luminaire which would be directed away from the calculation grid.

Calculation Grid In order to be able to test the photometric levels in the test room, a grid was measured out on the floor with equal spacing of 500mm between points. The grid squares were numbered as per Fig. 20 to facilitate the comparison graphs which will be used to analyse the results.

I Figure 20 Photo of Measurement Apparatus 12/04/14 Figure 21 AutoCAD Image of Measurement Grid

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Illuminance Meter The illuminance meter used for the measurements was an RS Components 203-013 digital light meter. The meter was provided by PGD Consulting Services and is calibrated by NATA (National Association of Testing Authorities) Australia.

A tripod with a lux meter attached (Fig. 22) was used to measure the illuminance at each point in the grid at a height of 800mm above floor level. In order to be able to take the measurements without interfering with the results, a small wireless camera was also mounted onto the tripod apparatus which viewed the lux level LCD display. As the apparatus was relocated to each new calculation point, the results could be viewed on a monitor (Fig. 23) in an adjacent room, ensuring no un-modelled objects or persons were affecting the measurements.

Figure 22 Photo of Measurement Apparatus 12/04/14

Figure 23 Photo of Remote Measurement Display 12/04/14

Global Positioning The longitude and latitude of the Test Room were checked on Google Earth and were as follows: • •

E 115° 51’ 54” S 31° 55’ 42.24”

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Orientation As two of the three scenarios would include day lighting as part of their calculations, it was vital to model as accurately as possible the exterior conditions. Firstly the orientation was checked using a compass to ensure a true magnetic north value was obtained. This was then adjusted to allow for the difference in Magnetic North and True North, which in Perth is only 1.5d west, which should make little difference but could be significant in some locations in the world and was worth verifying.

External Obstructions The external obstructions were measured and checked for reflectance values. These consisted of an adjacent house, a fence and the side wall of the house which formed part of the test room. The height of the test room relative to the external ground level was also recorded.

Sky Condition Most lighting simulation programs available will accommodate the CIE Clear Sky or Overcast Sky model for their daylight calculations. The CIE (International Commission on Illumination) also has produced an additional 15 standard sky models for use in daylight calculations. Out of the four programs being considered here, AGI32 is the only one whereby any of the CIE models can be selected. Radiance provides an option of four types based on conditions, whereas Relux will only consider either Clear or Overcast. Dialux provides an additional option above these two of Mixed Sky type. The sky condition was selected based on the weather conditions of the test day. Luckily, due to typical weather conditions in Perth, the selected sky type was Clear Sky and was common to all programs.

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Date and Time The date and time were recorded at the start of the calculation process and the time again at the end. It took approximately 10 minutes to record all 30 measurements per scenario.

The testing was carried out on the 12th of April 2014 between 15:38hrs and 16:20hrs.

Procedure Scene One - Daylight The blinds were completely opened so as not to block any of the glassed area. The time of the day was documented. The testing apparatus was positioned on the first calculation point. The room was vacated and the door shut. The illuminance level on the first calculation point was documented from the monitor in the adjacent room. The room was re-entered and the testing apparatus was positioned on the second calculation point. The process was repeated for all 30 calculation points. The time at the end of the testing process was again noted.

Scene Two – Daylight and Artificial Light The luminaire was positioned on the box and directed upwards towards the ceiling. The box's position was measured and noted. The luminaire was switched on and the testing apparatus was positioned on the first calculation point. The room was vacated and the door shut. The illuminance level on the first calculation point was documented from the monitor in the adjacent room. The room was re-entered and the testing apparatus was positioned on the second calculation point. The process was repeated for all 30 calculation points. The time at the end of the testing process was again noted.

Scene Three – Artificial Light The luminaire remained in its existing location. A blackout cover was positioned over the window to block any daylight. The white blinds were then shut, as these would be 48

modelled as a white plane positioned in front of the window. The luminaire was switched on and the testing apparatus was positioned on the first calculation point. The room was vacated and the door shut. The illuminance level on the first calculation point was documented from the monitor in the adjacent room. The room was re-entered and the testing apparatus was positioned on the second calculation point. The process was repeated for all 30 calculation points.

Results The results of the testing for the three scenarios are detailed below. The tables below represent the illuminance values in Lux. The boxes below are positioned as per the calculation grid in the test room.

A 490lx

B 527lx

C 553lx

D 553lx

E 558lx

F 490lx

G 521lx

H 553lx

I 569lx

J 571lx

K 502lx

L 547lx

M 591lx

N 607lx

O 598lx

P 523lx

Q 608lx

R 680lx

S 687lx

T 644lx

U 515lx

V 703lx

W 872lx

X 817lx

Y 672lx

Z 425lx

AA 761lx

AB 1122lx

AC 962lx

AD 596lx

Table 2 Test Room Measurement Values- Daylight Scene

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A 460lx

B 513lx

C 521lx

D 536lx

E 518lx

F 470lx

G 517lx

H 541lx

I 563lx

J 552lx

K 498lx

L 558lx

M 601lx

N 603lx

O 598lx

P 532lx

Q 629lx

R 719lx

S 728lx

T 662lx

U 530lx

V 742lx

W 948lx

X 878lx

Y 698lx

Z 429lx

AA 791lx

AB 1179lx

AC 988lx

AD 617lx

Table 3 Test Room Measurement Values - Daylight and Artificial Light Scene

A 46lx

B 51lx

C 52lx

D 52lx

E 49lx

F 52lx

G 57lx

H 60lx

I 61lx

J 58lx

K 58lx

L 65lx

M 69lx

N 69lx

O 65lx

P 63lx

Q 71lx

R 78lx

S 78lx

T 71lx

U 64lx

V 73lx

W 79lx

X 79lx

Y 73lx

Z 61lx

AA 68lx

AB 72lx

AC 73lx

AD 68lx

Table 4 Test Room Measurement Values - Artificial Light Scene

Comment on Results The above results are broadly what would be expected for each of the scenarios tested.

The results of scenario one highlight the high lux levels near the window, with these tapering off further from the window. The calculation points on the northern side of the room experienced higher lux levels than those on the southern side of the room.

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As expected introducing the artificial light source results in higher lighting levels on the calculation points directly surrounding the artificial light source but levels actually reduce below what was measured during the daylight only test as you travel further away from the luminaire. This is probably due to the time difference when the two sets of readings were recorded. As less daylight was available during this test the resulting light on the calculation points where the artificial light source is contributing less is lower.

The artificial light source scene has its highest values at the four calculation points surrounding the light source. The level of light falling on the meter then reduces evenly on the further calculation points.

Software Set-up Building the Model All plan dimensions of the test room and external obstructions were drafted in AutoCAD 2010 and imported into the various software programs. Using the snap function reduced the possibility of error in constructing many of the elements of the test scene.

After the geometry of the scene was completed, each surface was assigned a reflectance value based on the measurements taken of the actual test room. In addition, the transparency value for the glass was inputted.

The north alignment was then adjusted so that each scene alignment matched that of the actual test room.

Data Input On completion of the geometry input, each software program was saved three times to reflect the three different scenes to be modelled. For each of the two scenes which

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included an artificial light source, the ies file matching the artificial light source used was imported. This process is fairly straight forward in each of the programs with the only difference being that in Ecotect where it is necessary to insert an artificial light source in the scene first and then to assign the photometric properties of the file to that light source.

Calculation Grid The calculation grid was inserted in each of the programs to match the positions and heights of the measurements taken in the test room. In contrast to the other programs it was necessary to create 30 individual calculation points in Ecotect. This was required because the calculation grid in Ecotect does not produce specific illuminance values on completion of the simulation, rather just a range of values.

Running the Simulation DIALUX In order to simulate a “daylight” scene, it is necessary to create a new ‘light scene’ associated with the room in question. Parameters such as time and date are entered at this stage. When starting the calculation, the light scene required to be tested is selected and the option of ‘standard’ or ‘very accurate’ calculation methods are presented. (See Fig. 24 below) The ‘standard’ option which is advised as the recommended option was selected at first and the calculation time took just over 70 seconds to complete. However due to a significant deviation from the test room measured results, a second calculation was carried out utilising the more accurate option. This calculation took just over 10 minutes to complete. The comparison of the two sets of results differed very little. The results were copied to the Excel file to allow for comparison.

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After running the simulation for each of the three scenes, the following calculation times were recorded: •

70 second for Daylight only (standard calculation)

•

90 seconds for Daylight and Artificial Light

•

8 seconds for Artificial Light only scene

Figure 24 Dialux Calculation Window

RELUX In contrast to Dialux, the Relux calculation manager combines the ‘light scene’ set up values and the calculation option in one window. The type of calculation required is selected here from several options presented at the left of the window. If a scene which contains daylight is selected, then date and time, global positioning, north alignment and sky type can all be adjusted here. In addition, the precision of the calculation can be adjusted, with advice as to the appropriate settings provided. In my opinion this is far less complex and more intuitive than the Dialux procedure. There are also several parameters available to be manipulated based on expertise. (Fig. 25) After running the simulation for each of the three scenes, the following calculation times were recorded:

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•

10 second for Daylight only

•

10 seconds for Daylight and Artificial Light

•

5 seconds for Artificial Light only scene

Figure 25 Relux Calculation Manager Widow

AGI32 In order to simulate a scene with a daylight component, it is necessary to set up a ‘Daylight Study’, this is done through the ‘Daylight Study’ window, where location, north alignment, time and date and sky type are inputted. On completion of this process the simulation is ready to be initiated.

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Figure 26 AGI32 Daylight Study Parameters Window

AGI32 then offers two calculation options, direct only will only consider the direct component from a light source, while full Radiosity mode will consider all inter-reflected and direct components. (Fig. 26) After running the simulation for each of the three scenes, the following calculation times were recorded: •

24 second for Daylight only

•

35 seconds for Daylight and Artificial Light

•

10 seconds for Artificial Light only scene

ECOTECT/RADIANCE As Ecotect itself is capable of lighting calculations, (though basic by its own admission) it is necessary to export to the Radiance Software calculation manager in order for Radiance to carry out the calculations. Prior to this it is necessary to select each of the calculation points created in order to have a specific value assigned to each point.

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Figure 27 Ecotect Radiance Analysis Window 1of11

Once Radiance has been selected, you are brought to step 1 of an 11 step lighting analysis process. (Fig. 27) During this process time, date, sky type, views and accuracy settings are adjusted to suit the scene. The simulation was again run for each of the three scenes; the following calculation times were recorded: •

193 second for Daylight only

•

225 seconds for Daylight and Artificial Light

•

53 seconds for Artificial Light only scene

On completion of the calculation, it is necessary to import the results back into Ecotect to obtain the illuminance values associated with each calculation point.

Results The illuminance values for all calculation points for all scenes in all four software programs were recorded and presented in an Excel spreadsheet for comparison. The following graphs illustrate the results.

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Figure 28 Daylight Only Simulation Comparison Graph

Figure 29 Artificial and Daylight Simulation Comparison Graph

Figure 30 Artificial Light Simulation Comparison Graph

Photometric Comparison As can be seen from the above graphs, most programs performed well in all scenarios with the exception of Dialux where daylight was a factor. It is unclear as to why Dialux produced results which were so far outside of what was recorded and equally outside of any other program’s predictions. This shall be further addressed later in the section.

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In order to examine how close each of each of the programs’ simulated results matched that of the measured values, each calculation point was compared to its corresponding measured test room value. The difference between the two values was considered as a percentage of the measured value providing the percentage deviation on each calculation point. The average of all calculation points was then calculated providing an average percentage deviation for each program.

(Measured Point ‘A’ – Simulated Point ‘A’) x 100 / Measured Point A = Percentage Deviation at Point A Daylight Scene Fig. 31 below illustrates how close each of the program’s simulated results corresponded to that of the measured values. Radiance is the closest for the daylight only scene achieving results on average within 6% of the measured values. This is followed by AGI32 achieving within 9%, while Relux is within 13% of measured values. As mentioned, Dialux on average deviates by 56%.

Figure 31 Daylight Only Percentage Deviation Graph

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Daylight and Artificial Light Scene When considering the daylight and artificial light scene, the results are fairly similar with Radiance again achieving the least average deviation from measured results at less than 7%. AGI32 and Relux both achieve less than 10% average deviation at 9.6 and 9.8% respectively. As above, Dialux deviates from measured results at just over 51%. (Fig. 32)

Figure 32 Artificial and Daylight Percentage Deviation Graph

Artificial Light Scene In contrast to the above, when the daylight component is excluded from the simulation, the results differ slightly. Dialux is actually closest to the measured values with just over 8% average deviation. This is followed by Relux at 12% and closely followed by Radiance and AGI32 at 13.7% and 17.5% respectively. (Fig. 33)

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Figure 33 Artificial Light Percentage Deviation Graph

External Horizontal Illuminance As the error in the Dialux calculation could not be explained satisfactorily, some further testing was conducted to investigate possible reasons. As the various programs utilise different interpretations of the CIE Sky Model and as this has been highlighted as a cause for deviation between software programs’ simulated results, (Acosta, Navarro and Sendra, 2011) a further simulation comparison was conducted.

A simple external scene was modelled in each of the software programs whereby a single horizontal calculation point was positioned one metre above ground. The scene was given the coordinates of a local set of playing fields in Perth where no external obstructions existed. Each scene was simulated utilising both the CIE Clear Sky model and the CIE Overcast Sky model. Similarly to the test room above the actual site photometric measurements were recorded on the exact time, date and location of the simulated scene.

In addition to the measured and simulated scene parameters described above, the scene was simulated using the date and time of the original research test. On the day of testing the sky was again clear of any clouds.

The table below details the values simulated and recorded.

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Software Program

Sky Type

Illuminance

(Lux) Illuminance (Lux)

13/09/14

12/04/14

Dialux

Clear Sky

79,666 Lux

28,564 Lux

Dialux

Overcast Sky

17,551 Lux

8,822 Lux

Relux

Clear Sky

73,300 Lux

45,100 Lux

Relux

Overcast Sky

16,300 Lux

12,000 Lux

Radiance

Clear Sky

71,809 Lux

31,807 Lux

Radiance

Overcast Sky

15,409 Lux

7,714 Lux

AGI32

Clear Sky

94,000 Lux

41,687 Lux

AGI32

Overcast Sky

17,800 Lux

9,159 Lux

Actual

Measured Clear Cloudless Sky

112,100 Lux

Value Table 5 - Unobstructed Horizontal Illuminance Test Results

As can be seen from the above results, each programs’ predictions of unobstructed horizontal illuminance differ significantly to one another. Furthermore, depending on the time of year, the programs which exhibit one of the highest results in September may exhibit the lowest in April.

Discussion Both of the scenes which considered daylight when simulated produced similar sets of results from the various programs, with Radiance performing best and Dialux performing least well. In contrast, the artificial light scene differed in which programs performed best.

It could therefore be concluded that the inclusion of daylight in a simulation project will have a bearing on which is the best program to use for that project. Radiance has been widely referenced and validated in numerous studies, most of which consider daylight simulation. It is maybe not surprising that Radiance has produced the most accurate results in this research when daylight is a factor. Radiance is the only software program out of the 61

four which uses a Backward Raytracing algorithm. All of the other tools utilise a Radiosity algorithms as their primary calculation method. Just examining the simulated values in the test room suggests very little difference between the Radiance results and that of Relux/AGI32.

The follow on unobstructed sky illuminance test highlighted the significant differences between software programs and their interpretations of the clear sky model used and also how these can change during the year. Interestingly, Radiance and Dialux produced very similar results in this test for the time and date of the original simulation, despite these programs producing the closest and furthest results compared to measured values respectively.

If Dialux and Radiance are predicting similar sky illuminances, then perhaps the vast differences in internal simulated light levels are due to the difference in calculations methods. If this is the case, then it would suggest that the reason for the similar results observed from both Relux and AGI32 are not as a result of an accurate interpretation of reality but more from an overestimation of the sky illuminances coupled with an underestimation of internal and external reflections as a result of the radiosity method.

In reality, there are just too many variables and unknowns to be able to make any confident predictions as to why the programs are producing the results they are.

When considering all three simulated scenes, there does not appear to be any correlation between calculation times and accuracy. Radiance took the longest for all scenes followed

by Dialux, AGI32, with Relux taking the shortest time to simulate. Radiance’s simulation time could also be attributed to the Raytracing process taking longer to complete than the Radiosity process. (Tobler, 1997)

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Dialux produced the most accurate results when only considering artificial light with AGI performing least well. It is worth noting that AGI32 is the only software which is not free to download, therefore price certainly does not equate to accuracy in this instance.

Personally I found Dialux to be the simplest program to use from a modelling perspective for the scene in question. Relux is a little unintuitive in how room and objects are manipulated. AGI32 is also unintuitive when modelling windows and doors, although I am sure with practice these would become second nature. As the model needed to be created within Ecotect for the Radiance simulation, the process of constructing the model differed significantly compared to the other programs. Ecotect requires the model to be created in a 3D model space which takes practice to become efficient in. Persons with 3D modelling experience would no doubt find this much simpler than the average professional.

That said; once the modelling is complete the calculation process, especially for the daylight scenes is easier in AGI32 and Relux.

One further observation from the above test is the difference of the measured value to that of all simulated values for external illuminance. It is worth noting that the CIE sky models are intended to provide a means of software programs to predict lighting levels for design purposes and therefore some averaging of factors affecting this occurs. As a lighting design incorporating daylight has to be relevant for a period of years and not just a snapshot in time, it is perhaps unrealistic to expect very close results when only considering a specific time and date in a scene incorporating daylight.

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Limitations Although every effort was made to minimise errors in the simulation process, it is not always possible to eliminate these totally. The following section will highlight all these areas where some deviation could have occurred.

Window Transparency The transparency of the glass in the window could not be tested and therefore a typical value was used as described above. This would have allowed for an additional margin of error.

Geometry Input Some room element would not have been modelled; these would have consisted of door handles, window ledge and most notably the existing light fitting. Although some measures were taken to reduce the errors associated with the light fitting, some deviation would be expected.

Time used for Simulation Calculation As the actual photometric measurements were taken over the course of approximately a 10 minute period, the natural light levels would have adjusted slightly in line with the sun’s position in the sky. A particular reading at the start of the process would differ slightly if the same point were measured again at the end of the process. For the purposes of the software simulations the median time was taken as the correct time. For example if the measurement process was carried out between 15:38 and 16:51, then 15:44 was used as the time inputted into the software.

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Measurement Instrument Some deviation can be expected from calibration errors of the measurement instruments.

Visual Assessment of Reflectance Values As previously detailed the reflectance values of the test room surfaces were assessed using a reflectance card system and not measured with calibrated instruments. This could potentially result in a deviation from actual values.

Voltage Fluctuations Affecting Artificial Light Source Output It is possible that voltage fluctuation could have caused variations in the light output during the course of the testing, therefore affecting the values measured at certain points.

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Chapter 5 Conclusions The primary purpose of this research was to examine a range of lighting simulation programs from two perspectives, that being ‘popularity and use in industry’ and in ‘calculation methodology and ability to simulate some simple scenes’.

Section Two of this report offers the results of an online survey which provides valuable insight into the use of the programs in industry today. The analysis and discussion provided at the end of this chapter is solely concerned with this first objective.

The survey results offered information on a number of aspects with respect to users and their use of lighting simulation software including respondents’ choice of program, use of program, location, profession, experience level, frequency of use and others. Although all discussion provided was intended to meet the objective of this phase of the project, the primary conclusion is that Dialux is by far the most widely used lighting simulation tool across the globe, with its highest level of use being in Europe and amongst engineers. The reasons for this are demonstrated to be that many Dialux users are amongst the less experienced and have likely only used Dialux and perhaps Relux. As has been highlighted in recent surveys the use of this type of software is on the increase which may explain why many of the respondents of the survey have described their experience level as being less than 10 years. (Fitz, Reinhart, 2004) However, the survey also highlights that although being used by a much greater number, when users’ experience level increases and as they are exposed to other programs such as AGI32, Dialux is often replaced by these programs as the tool of choice.

The key objectives of the second phase of this project were to compare the programs in their calculation methodology and to test their ability to simulate various simple scenes.

The first of these objectives were dealt with during the literature review section and established that one of two main calculation algorithms are used in each of the lighting 66

simulation programs being examined. Radiance utilises the Backward Raytracing technique while, Relux, Dialux and AGI32 utilise Radiosity for their primary calculation. Relux also has the option of utilising the Radiance Backward Raytracing algorithm if selected.

The simulation comparison has highlighted that in the Daylight Only Scene and the Daylight and Reflected Artificial Light Scene, all programs on average produced results within 10% of their mean value, with the exception of Dialux.

During the Reflected Artificial Light Scene, all programs produced results within 16% of their mean value.

There are a number of factors which may influence the difference in results produced.

These are geometry errors when inputting the different models, differences in how each program interprets the CIE sky model, and of course the calculation algorithms used.

The comparison of the programs' photometric results and that of the measured values has indicated that Radiance is more accurate than the others when considering daylight. This conclusion is further supported by the literature review which has cited many previous studies validating Radiances ability to simulate daylight accurately. As radiance is the only program to utilise the Backward Ray tracing algorithm, one could surmise that this algorithm is superior to Radiosity for daylight calculations.

The unobstructed external sky illuminance test proved that there are significant differences between software programs and their interpretations of the standard sky models and also how these can change during the year. This testing rather than providing explanations as to the results observed has in fact added to the uncertainty of what is happening during the calculations process.

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In contrast to the day lit scenes, the reflected artificial light scene produced different results, indicating Dialux being the most accurate when compared to the actual measurements.

However, I would be cautious about any such deductions or claims of accuracy. Not only does one have to consider the possible errors mentioned above with respect to the programs' comparison, but when considering a comparison with measured data, the list of possible errors grows quite substantially. Errors such as Surface Reflectance deviation, Glazing Transmission deviation, Instrument Calibration errors, Voltage fluctuations affecting light output and variations in daylight availability will all add to the possible overall margin of error.

Each of the above possible errors could have an accumulative effect or a cancelling out effect, therefore making it very hard to determine the accuracy of any one program over another. That being said the final objective of this research was not to determine the most accurate program but to compare the simulated results with that of measured values and to offer possible explanations for this.

The results of the survey suggested that most lighting software is used to simulate interior scenes without a daylight component and the above research shows that this can be achieved with some confidence by all programs tested. When considering a daylight component in any simulation, the outcome may be somewhat uncertain.

It is likely that the only way to properly compare these programs in the context of photometric validation is to construct a purpose built test room with all known properties located in an area with no external obstructions. Only by eliminating all the possible errors completely would one then be able to draw some reliable conclusions on the accuracy of these tools.

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Further Research Due to time constraints when conducting this research, some additional testing and investigation which may have produced interesting results could not have been undertaken. Further research in the following areas would be of benefit in understanding the limitations of these software programs.

•

Additional light scenes including direct light from single source and multiple sources

•

Additional room types including larger rooms and multiple openings

•

Comparison of simulated results using the Relux Radiance Ray Tracer with the standard Radiosity calculation method

•

Further research into how each of the programs interpret the CIE sky models and how this can affect the simulated values – this should examine comparisons of different software products and their simulated values for dates and times throughout the year.

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References Acosta, I., Navarro, J. and Sendra, J. J. (2011) Towards an Analysis of daylighting simulation software Energies Vol.4 pp 1010-1024 Altman, K. and Apian-Bennewitz, P. (2001) Report on an investigation of the application and limits of currently available programme types for photorealistic rendering of light and lighting in architecture [online] Available at: http://www.licht-akademie.de Accessed: 12 November 2013 Amorim, C. N. D and Christakou, D. E (2005) Daylighting simulation: comparison of software for architect’s utilization Building Simulation 2005 Ninth International IBPSA Conference pp 183-190 Aries, M.B.C., Henson, J.L.M. and Ochoa Morales, .C.E. (2010) Current perspective on lighting simulation for building science Proceedings of IBPSA-NVL 2010 Event, Eindhoven: pp 1-9 Aries, M.B.C., Henson, J.L.M. and Ochoa Morales, .C.E. (2012) State of the art in lighting simulation for building science: a literature review Journal of Building Performance Simulation Vol.5 pp 209-233 Ashdown, I. (2001) Eigenvector Radiosity University of British Columbia Augenbroe, G. (2002) Trends in building simulation Building and Environment Vol.37 pp891-902 Campbell, K., Lau, S., Ligocki, T. and Robertson, D. (1999) Parallelization of radiance for real time interactive lighting visualisation walkthroughs Proceedings of the ACM/IEEE SC99 Conference IEEE Computer Society CASRO (2011) Code of standards and ethics for survey research [Online] Available at: http://c.ymcdn.com/sites/www.casro.org/resource/resmgr/casro_code_of_standards.pdf (Accessed: 03 September 2014) Christakou, E. and Silva, N. (unknown) A comparison of software for architectural simulation of natural light University of Brazil Christoffersen, J., Hvass, M., Iversen, A., Johnsen, K., Jorgensen, M., Osterhaus, W. and Roy, N. (2013) Daylight Calculation in Practice Danish Building Research Institute Copenhagen: Fitz, A. and Reinhart, C. (2004) Findings from a survey on the current use of daylight simulations in building design Energy and Buildings Vol.38 July 2006 pp824-835 Feriadi, H., Hien, W. N. and Poh, L. K. (2000) The use of performance based simulation tools for building design and evaluation – a Singapore perspective Building and Environment Vol.35 pp709-736 Galasiu, A. D. and Reinhart, C. F. (2008) Current daylighting design practice: a survey Building Research and Information Vol.36 (2) pp 159-174

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Hebal, J. H. and Kota, S. (2009) Historical survey of daylighting calculation methods and their use in energy performance simulations Proceedings of the Ninth International Conference for Enhanced Building Operations November Ibarra, D. I. and Reinhart, C. F. (2009) Daylight factor simulations – how close do simulation beginners ‘really’ get? Building Simulation 2009 IBPSA Conference pp 196-203 Ibarra, D. I. and Reinhart, C. F. (2013) Teaching daylight simulations – improving modelling workflows for simulation novices Proceedings of IBPSA pp 1126-1135 August Kensek, K. and Suk, J. Y. (2011) Daylight factor verses daylight availability in computerbased daylighting simulations Journal of Creative Sustainable Architecture and Built Environment Vol.1 pp 3-14 Li, D.H.W. and Tsang, E.K.W. (2005) An analysis of measured and simulated daylight illuminance and lighting savings in a day lit corridor Building and Environment Vol.40 pp 973-982 Nagakura, T., Ng, E.Y.Y, Poh, L.K, and Wei, W. (2001) Advanced lighting simulation in architectural design in the tropics Automation in Construction Vol.10 pp 365-379 Stravoravdis, S. (2013) Lighting Offices with LEDs: A Study on Retrofitting Solutions Welsh School of Architecture Relux (2010) Relux light simulation tools – Fit for Raytracing [online] Available at: http://www.relux.biz/pdf/09_RaytracingManual.pdf (Accessed: 06 July 2014) Reinhart, C. R. and Walkenhorst, O. (2001) Validation of dynamic radiance-based daylight simulations for a test office with external blinds Energy and Buildings Vol.33 pp 683-697 Roy, G. G. (2000) A comparative study of lighting simulation packages suitable for use in architectural design Murdock University SLL (2001) Lighting Guide 11 Surface reflectance and colour Society of Light and Lighting & National Physical Laboratory Norwich: Stravoravdis, S. (2013) Lighting Offices with LEDs: A Study on Retrofitting Solutions Welsh School of Architecture Tobler, R. F. (1997) Radiosity – Raytracing [online] Available at: https://www.cg.tuwien.ac.at/research/rendering/rays-radio/ (Accessed: 26 July 2014)

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Bibliography Ashdown, I. (2002) Radiosity: A Programmers Guide New York: John Wiley and Sons CASRO (2011) Code of standards and ethics for survey research [Online] Available at: http://c.ymcdn.com/sites/www.casro.org/resource/resmgr/casro_code_of_standards.pdf (Accessed: 03 September 2014) Herkel, S. and Reinhart, C. F. (1999) The simulation of annual daylight illuminance distributions – a state of the art comparison of six Radiance based methods Energy and buildings Vol.32 pp 167-187 Huang, C. H. (2011) An integrated scalable lighting simulation tool Carnegie Mellon University Hui, S. C. M (2003) Effective use of building energy simulation for enhancing building energy codes IBPSA Building Simulation 2003 Conference pp 1-8 Khoshroonejad, S. (2010) A comparison of daylight prediction methods Gazimagusa: Eastern Mediterranean University Lee, J., Anderson, M., Sheng, Y. and Cutler, B. (2009) Goal based daylighting design using an alternative simulation method Building Performance Simulation Conference July Love, J. A. and Navvab, M. (no date) A comparison of photometric modelling and computer simulation techniques for daylight prediction under real sky conditions pp 97-106 Oh, S. (2013) Origins of analysis methods in energy simulation programs used for high performance commercial buildings Texas: Texas A&M University Reinhart, C. F. and Wienold, J. (2010) The daylighting dashboard – a simulation based design analysis for day lit spaces Building and Environment pp 1-25 August Relux (2010) Relux light simulation tools [online] Available at: http://www.relux.biz/index.php?option=com_content&view=article&id=216&Itemid=189 &lang=en (Accessed: 12 November 2013) SLL (2012) The SLL Code for Lighting London: CIBSE Sobh, T. (2008) Advances in computer and information sciences and engineering Bridgeport: Springer Stewart, K. and Donn, M. (2007) Daylight simulation for code compliance: creating a decision tool Building Simulation pp 1189-1196 Tobler, R. F. (1997) Radiosity – Raytracing [online] Available at: https://www.cg.tuwien.ac.at/research/rendering/rays-radio/ (Accessed: 26 July 2014)

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Appendix 01 Survey Results Question 1 – Which Best Describes the Location Where you Work

Work Location 17%

22%

North America South America Europe

1%

1% 6%

Middle East

8%

Asia

45%

Africa

Question 2 – Which Best Describes You

Profession

Electrical Engineer Lighting Designer

6% 3%

6%

6%

Architect 37%

Interior Designer Energy Consultant

0% 8%

Software Developer

3%

Academic 31%

Lighting Product Sales Rep Other

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Question 3 – Which of the following Simulation Software Have you Previously Used

% of Total Respondents

Lighting Simulation Software Previously Used 100 80 60 40 20 0 Dialux

Relux

Radiance Radiance 3rd party

AGI32

Other

Question 4 – Which Simulation Software Had you Not Previously Heard Off

Lighting Simulation Software Not Previously Aware Of 2% 4% Dialux 23% 50%

Relux Radiance AGI32

21% Heard of them all

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Question 5 – Which is your Simulation Software of Choice

Lighting Simulation Software of Choice Dialux 16%

Relux 40%

Radiance

18% Radiance 3rd party

5%

7%

AGI32 14% Other

Question 6 – How long have you been using Lighting Simulation Software

Lenght of Time Using Lighting Simulation Software

9%

5% 25%

Less than 5 Years Between 5 - 10

20% Between 10 - 15 41%

Between 15 - 20 Longer than 20

75

Question 7 – Which Best Describes the Reasons Why you Use the Software you Do

Reasons for Using Preferred Software Tool It’s the 1st softare I used 11%

15%

9% 8% 29%

I tried more than 1 but feel this is mores suited to work I tried more than 1 but feel this one is the best I hav researched several and have selected this one It is free to download

15% It is the quickest for the projects I moslty use it for Other

13%

Question 8 Which Describes your Current use of Lighting Simulation Software

Use of Multiple Software Tools

I use only one tool 46% 54%

I use more than one depending on application

76

Question 9 Which Best Describes your Proficiency Level

Proficiency Level 6%

Basic 33%

Medium Advanced

61%

Question 10 How Often do you use Lighting Simulation Software

Frequency of Use of Lighting Simulation Software 9% Almost every day 17%

42% once a week once a month 32% 2-6 time a year

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Question 11 Which do you Believe the Most Important Feature to Be

Most Important Feature 3%

Accurate Results

8% Visually accurate renderings 18%

Ease of use

6%

65%

Compatibility with other software Other

Question 12 Which Scenes Do you Simulate Most

Which Scenes do you Simulate Most 1% Indoor without daylight 29%

Indoor scene with daylight 47%

Exterior scene All of the above equally

6% 17%

Other

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Question 13 – What Prevents you from Using the Software More Often

Obstacles to More Frequent Use of Software 3%

Lack of Training

2% 6%

too Complex Time Constraints

16%

Client does not pay for it 10% Cost of Software

59% 4%

N/A I use it as often as required Other

Question 14 – What Do you Consider to Be the Most Important Recent Improvement

Most Important Improvement More user friendly 8% More Accurate

13% 43% 20%

Better Renderings More compatible with other software

16%

Other

79

Question 15 – How Do you Most Use the Outputs from Your Simulations

How do you Most Use the Outputs To show clients 5% 19%

For research 30% For code compliance/meet regulations To improvee designs 9%

37% Other

Question 16 –Which Best Describes the Methods of Training you Utilise

Methods of Training 2%

11% Seff Thought Taught or helped by others

20%

Attended in-house training 67%

Attended external training

80

Question 17 – How accurate do you believe the results of simulation software to be

How Accurate Do You Believe Lighting Simulation Software To Be 2% 17%

2%

20-40% 40-60%

10%

60-80% 80-90% 25%

90-95%

44%

95-100%

Question 18 – Are you Familiar with the Algorithms Used in Lighting Simulation Software

Are You Familiar with the Algorithms Used

46% 54%

No Yes

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