Parametric UD on Topography

Cheng Zixuan, Cui Yuechen, Wang Xinran, Zhang Jin

For further details please get in touch with:

• Cheng Zixuan (u3589388@connect.hku.hk)

• Cui Yuechen (cuicui@connect.hku.hk)

• Wang Xinran (alician@connect.hku.hk)

• Zhang Jin (zhangji0@connect.hku.hk)

• Siddharth Khakhar (khakhar@hku.hk)

2.8 Introduction and Background

The GW report includes an understanding of the research method, existing literature review, research techniques involved, types of urban research that can be explored etc.

The focus of the report is to demonstrate and report on the use of research techniques.

Parametric design

Before the design is completed, many details and indicators of the design need to be debugged and analyzed. So the model needs to be modifiable. Parametric design is to quantify these variables into arbitrarily adjustable parameters and assigns values. Parametric design can optimize the design by designing a complete design logic and adjusting the variables in it.

Generative design

Refers to the need to generate logic through some logical steps in the design, and by quantifying the logic, the computer can assist the designer to extend the simulation of this logic, assist the human brain to generate the scheme, and quickly iterate or optimize the scheme. program form (Caetano I, 2020).

Algorithmic design

The algorithm design is mostly covered in this pd and gd in the literature, (TERZIDIS, 2004) In this paper, the authors identify ad as a design method based on computer programs, such as building code and building programs, in which the designer directly manipulates the code to design, thereby reducing the limitations of modeling applications (Queiroz N, 2005).

2.9 Parametric design platforms

Parametric design is a mathematical tool, which is the result of adaptive logic processing of selected information and data. Using the parametric platform, the design becomes a dynamic model, which can quickly respond to the input provided by the designer. Therefore, the parametric modeling system is rooted in algorithm logic and relies on human-computer interaction tools to show the process of combining algorithm logic with parametric modeling. Most parametric modeling relies on rhino GH and rhino Revit platforms. For Revit, it is parameter driven software, that is, all elements can be modified by changing parameters. Family is the foundation of Revit, and the construction of all entities depends on the family, so the family must also be parametric, that is, the parameter can be used to modify the element. But because of this, it is difficult to modify and adjust the set ethnic groups in Revit. For rhino GH, grasshopper 3D converts the algorithm logic into visible command components. People can manipulate the command components to realize the corresponding model and carry out personal parametric design.’

2.10 Parametric design limitations in urban design

The parametric method of urban design requires the designer to select data of different properties according to the predetermined objectives (Fusero P, 2013),these data represent the factors that restrict the design process. This is also a major advantage of parametric design, which can provide an effective and controlled influence process and visually show the audience how the modification of selection parameters can affect the whole large-scale system. These data may be strict urban parameters, such as building or environmental land and construction density. They may be bioclimatic factors, such as the thermal state of the sun or the wind speed in urban canyons. They may be data related to building energy efficiency, such as real estate value and urban safety level.

Parametric tools are applied to the simulation and research of related urban design. But this does not mean that parametric tools can create a perfect system to predict people’s behavior in urban design. Intangible factors such as cultural background, social development and economic impact are rarely involved and considered in the parameterization process.

On the one hand, it is difficult to ensure the accuracy and accuracy of the data used, so generally speaking, the parametric modeling system generally generates an experimental model result. For the data that can be accurately quantified in the urban environment, such as the construction density of urban or environmental density, this kind of data input into the parametric system can truly simulate the data in the predicted environment; However, for the data related to bioclimate and building energy efficiency, it is difficult to accurately predict through parametric design because such data cannot be established on the basis of accurate mathematical quantitative formula research and cannot accurately and objectively quantify the corresponding index parameters. For example, some indexes in the parameter model are calculated by computer program, such as environmental comfort. There is no clear evidence of absolute accuracy. In fact, environmental comfort includes multiple parameters, such as solar height, season and temperature, air pressure, wind speed and direction on a specific date (Zhang Y, 2021). These factors are not included in the modeling script. Parametric technology can help improve environmental quality by modeling, simulating, and evaluating environmental urban form, but it cannot be comprehensive and accurate simulation analysis.

On the other hand, human behavior is affected by individual differences and changes with external influences. Many relevant influencing factors, such as people’s psychological activities, are not reflected by parameter methods. In addition, parametric design is not the only solution to all urban environmental problems and can only play a relevant role in the early conceptual stage. Overemphasizing the results of parametric modeling may lead to the neglect of some subjective or difficult to quantify objective factors n the decision-making process. The parametric modeling system has the characteristics of high efficiency, automation, and flexibility. It is an alternative method to assist decision-making, rather than completely replace the manual method. There is no evidence that parametric model provides a better solution than traditional manual work. Therefore, the parametric method of environmental optimization may be the most effective in the conceptual stage of urbanization, in which it provides simulation and evaluation based on parameters and data.

In the long term, parametric method will bring more convenient and dynamic technical support for urban environmental development, because parametric urbanization does have the ability to support the design optimization of complex urban areas. However, at present, there is more consensus that manual method can carry out better form design solutions than parametric design, so parametric design generally appears in the conceptual stage of scheme design. If you want to fully realize parametric technology for design, further research is needed.

2.11 Research background

“Some cities built on steep slopes, such as San Francisco, because of the lack of respect for the terrain, the rectangular planning makes the local residents constantly expend energy and time, suffer economic losses every day, consume many tons of gasoline and coal, not to mention, and destroy the natural scenery of the mountains; these natural landscapes should be fully utilized to make the city plan very beautiful.” (Van Ravenswaay, 1991)

Therefore, whether it is a mountainous or plain city, it is necessary to consider how to adapt to the natural terrain. The consideration of terrain should be considered from the stage of urban overall planning, and then gradually adjusted and refined in the stages of control regulations, architecture until construction drawing design, and landscape, architecture, infrastructure, roads, and water conservancy designers should consult and coordinate with each other to obtain harmonious, unified, natural, and artistic solutions. This is a very basic aspect of “natural urban design”.

Regional urban design often requires the design of urban forms within thousands of hectares, and at the same time, the comprehensive configuration of industry, transportation, ecology, landscape, places, infrastructure, etc., will eventually be presented in urban form(Schneider et al., 2011). Driven by the concept of urban development such as low-carbon and sustainable development, urban design is also paying more and more attention to the adaptation and effective use of the original natural environment. The use of digital analysis and simulation tools to interpret relevant geo-meteorological data is undoubtedly a scientific and effective means to help the design achieve the maximum conservation of natural resources.

However, urban design work cannot be achieved through complete rational derivation. Absolute efficiency does not necessarily lead to the emergence of pleasant and personalized urban forms. The design process south also requires a large number of designers to integrate and reflect the subjective creative design intentions. Some degree of “waste” may lead to greater potential or intangible benefits. Although digital tools can help objective judgment and improve design efficiency, how to take into account the creativity and empirical judgment of designers in the process of use is a topic to be handled in the development of digital tools for urban design.

Framework for parametric design on topography

Unlike designs on flat land, designers should consider the many influencing factors contained in the mountain into the design process, such as topography, landform, water distribution, climatic conditions, etc. This process will be more complex than parametric design on flat ground.

Taking terrain as an example, natural terrain is divided into two types: “large terrain” and “small terrain”. “Large terrain” refers to the shape of a large area of the land surface in a considerable area, generally according to the characteristics can be divided into shallow hilly areas, shallow hills and deep hills, etc., if the division scale is larger, it is also divided into land and ocean, and land is divided into plateaus, mountains, hills, plains and so on(Figure3). “Small terrain” is a local part of the large terrain, such as the “mountainous” in the large terrain can be divided into hills, hills, mouths, cols, platforms, canyons, basins, mountains, etc., a wide variety of types(Spirn, 1984). The natural terrain in turn has an impact on the solar radiation conditions, temperature and humidity conditions and wind flow fields of the cities on them, which can significantly affect the urban environment. The absolute elevation of the terrain affects the intensity of the city receiving solar radiation, and the relative slope and aspect of the terrain can change the shadow length of the building on it, the building located on the south slope, the shadow becomes shorter and the building on the north slope, the shadow becomes longer, the slope is larger, the more obvious the change.

Therefore, before the design begins, various natural influencing factors should be included in the scope of the impact on the suitable area. Detailed design guidelines are summarized in advance. for subsequent parametric design work.

2.13 Software used

The software used in this design study is Rhino and Grasshopper. Rhino is a 3D modeling software that is widely used in industrial design, architectural design and urban design. Grasshopper is a parametric built-in plugin for the Rhino platform. Its advantages are fast interaction efficiency with rhino modeling platform and user-friendly programming, its limitation is that it requires a certain grasshopper programming foundation.

ArcGIS can also be used to perform this series of analyses and calculations. ArcGIS has powerful geographic data management and analysis capabilities, but the disadvantage is that ArcGIS has a lower degree of freedom. For designers, Grasshopper allows designers to modify analysis algorithms and drawing methods, and Grasshopper is more efficient and intuitive for 3D analysis.

2.14 Topography understanding, creation, and analysis

The software used in this design study is Rhino and Grasshopper. Rhino is a 3D modeling software that is widely used in industrial design, architectural design and urban design. Grasshopper is a parametric built-in plugin for the Rhino platform. Its advantages are fast interaction efficiency with rhino modeling platform and user-friendly programming, its limitation is that it requires a certain grasshopper programming foundation.

ArcGIS can also be used to perform this series of analyses and calculations. ArcGIS has powerful geographic data management and analysis capabilities, but the disadvantage is that ArcGIS has a lower degree of freedom. For designers, Grasshopper allows designers to modify analysis algorithms and drawing methods, and Grasshopper is more efficient and intuitive for 3D analysis.

Topography generation using Rhino/Grasshopper

First, we need to obtain the elevation information (contour lines, contour points, elevation text, etc.) required to create terrain. This elevation information generally comes from shp. format (gis) data or dwg. format (cad) data, of which dwg. format data can be directly imported into rhino while shp. can be imported via the GH plugin @IT (@IT is a free GIS plugin for Grasshopper for parsing geospatial datasets, available for download via food4rhino: https://www.food4rhino.com/en/app/it).

After importing, select the data used to generate the terrain through the curve of the site boundary, and convert all the elevation data into point data, generate the mesh through Delaunay Mesh, and then optimize the mesh structure through point projection to complete the terrain mesh creation.

Topography analysis

Slope angle in degrees (0-10, 10-20 etc). The slope of the terrain is calculated by calculating the angle between the normal vector and the z vector of each subdivision mesh.The program allows to change the range of slope filtering, the mode of mesh shading (graded shading or gradient shading).

Slope direction (Aspect)

The aspect of the terrain is obtained by subdividing the normal vector of the mesh, and the mesh is colored according to the orientation data. The program allows modification of the number and extent of aspect filters.

Topography heights

The height of the terrain is calculated as the z-value of each subdivision mesh control point (mesh shading) or the z-value of the contour lines (curve shading). The program allows to change the mesh shading mode and contour height difference.

Rain water run-off primary and secondary channels

Rain water run-off analysis is a simulation of the real physics of rain fall and runoff. The whole simulation process can be simplified as the process of raindrops moving along the tangential direction of the mesh’s gravity. The simulation process is carried out through the animation control of the sliding kangaroo component. The program allows modification of dynamic parameters such as rain gravity, but only affects the analysis process and not the analysis results.

In the landscape analysis of large-scale areas, based on the results of rainwater runoff, these water catchment areas (landscape nodes) can be connected through algorithms to form rivers (landscape corridors). These abstract corridors can provide a relative sense for urban design sites. Science-based Landscape Network.

Water catchmen areas

Stormwater runoff lines and catchment points (final locations of stormwater points) are available after the Rain water run-off simulation ends. After that, we can rate the catchment area. The rating standard is the number of catchment points. The more the number of rainwater points, the more prone to flood disasters in the area. The program can adjust the catchment area grading criteria based on the number of stormwater points.

Flooding analysis

Flooding analysis performs risk assessment by simulating flooding after a river rises. The program allows to modify the distance the river submerged rises.

Bison plug-in for Grasshopper

Bison is a free plugin for terrain analysis based on rhino and grasshopper (downloadable via food4rhino: https://www.food4rhino. com/en/app/bison). Analysis tools include slope and aspect visualization, cut/fill calculations, watershed modeling, and more, while editing components transform meshes based on curves and points. Bison also includes tools for importing landscape meshes, triangulation, and resampling, as well as components for annotating plans and cutting sections. For example, a continuous section along a curve.(

2.15 Multi-criteria analysis framework for design

The above evaluation of terrain grids is based on grid analysis of unified standards, so multivariate analysis can be superimposed to obtain comprehensive evaluation results. Taking the assessment of suitable construction areas as an example, factors such as slope, water catchment area, and flood risk can be superimposed to evaluate the suitability of the terrain subdivision mesh.

For undeveloped slope steepness of more than 40%, do not disturb portions of the project site within 50 feet (15 meters) and the horizontal distance to the toe of slope is 75 feet (23 meters). To formulate contract, conditions and restrictions, development agreement or other binding file, permanent protection all steep slope. The following requirements apply to slope is greater than 15% of the project site.Undeveloped slopes steeper than 40%, do not disturb parts of the project site in one of the highest 50 feet (15 meters) of the slope and the level of 75 feet (23 meters) toe of slope.

2.16 Developing design guidelines

Different natural environmental conditions in the site will have different degrees of influence on the distribution of suitable areas, of which slope, hydrology and flooding are the most significant. Therefore, we start from three perspectives and summarize the guide-lines in details. For the purpose of subsequent calculations, the suitable construction range and the development capacity distribution are obtained.

Slope construction guideline

The original intention of this guideline is to establish buildable areas and buffer zones for steep mountain slopes by dividing slope ranges. At the same time, we intend to minimize soil erosion to protect the habitat environment of the construction area, and reduce the pressure on the water system by protecting steep slopes in a state of natural vegetation.

Two related slope guidelines are shown as follow: a) Required restoration and protection areas of slope

The following requirements apply to slope is greater than 15% of the project site. Ensure that existing slope is less than 15% of the share is greater than the existing development footprint on the slope is greater than 15% share of the project site. According to the table below, before any existing, developing the steepness of slopes of more than 15%, with local plants or non-invasive adapt to restore slope area.

Management practices related to building placement on slopes

Based on mountain terrain, such as mountain, foothill, and floodplain area, first judge whether the high-risk area within the area is more than or equal to 3 according to water catchment analysis. For mountains, if the high-risk area is more than or equal to 3, it will be classified as A. intensity reservoir type; for foothill, if the high-risk area is more than or equal to 3, it will be classified as B. pond type; for floodplain, it is classified as C. wetland type.

For plots with a high-risk area less than 3, regardless of its terrain type, the areas more than or equal to 3 will be classified as D. River / stream type, terrain less than 3 is classified as Grassland and tree type.

Reference and classification framework as follows:

Source: Land of Sky-MRSSPS Final report

Water catchment guidelines

According to the previously proposed water run-off analysis and water catch analysis, we can analyze the hydrological type of the site according to the current catchment degree and the number of medium and low-risk areas. The following figure is explained as an example.

Source: NNBF-guidelines-2021: Water management Reference

The previous study analyzed the slope and water catchment based on digital analysis, the final part is the study of flooding of rivers in geographic analysis. Rivers have some impact on the land on both sides because of the phenomenon of rising and falling of the flooding

In the assessment of the flooding impact, we have two key heights to assess, one is seasonal top height and 50 years top height of flood, so these two heights become the criteria for assessing the flooding area. And then we are roughly divided into three categories according to the collected terrain in Hongkong, In the diagram I use the length of A to show the different. They have three main types, one is that the river has a significant layer difference with the land, the second is a flat slope between the river and the land, and the third is that there are some depressions between the river and the land.

In the first type, the river and the land have a clear boundary, so at high tide, even the largest tidal difference will not flood into the land, so this has a clear buildable area and a not suitable -construction area, so it is possible to set up a permanent landscape between the river channel and the construction area, and enhance people's spatial experience close to the river

2.17 Conclusion and Discusison

Parameterization can liberate productivity. Parametric analysis is applicable to various types of terrain and sites. It can deepen the understanding and understanding of the site through early analysis and guide the later site design. The use of parameterization in UD project is more conducive to a basic understanding of this large project site, which are suitable for construction areas and which can be used as environmental protection areas, which can provide designers with early design entry points.

As students majoring in design, we think rhino-grasshopper workflow is relatively more operable and does not need programming background knowledge like python. Grasshopper battery pack has written a lot of operation commands, which only needs to connect the battery according to logic, which is very convenient. At the same time, grasshopper can also use programming language to assist design, which is a more powerful platform.

The parametric generative urban design generation method can split the generation process into multiple steps according to the basic process of the urban design project, and use an open generation method to improve the designer’s control over the generation process. This allows the generation tool to be integrated into the design process in a more friendly way, improving design efficiency while ensuring that designers have enough creative space.

2.18 List of Reference

• B., K., 2003. Digital morphogenesis. In: Architecture in the digital age: Design and manufacturing. s.l.:s.n., pp. 12-28.

In the second type, because the submerged area is large, so the wetland park and ecological conservation area can be used to alleviate it

• Caetano I, S. L. L. A., 2020. Computational design in architecture: Defining parametric, generative, and algorithmic design. Frontiers of Architectural Research, 1 Jun, pp. 287-300.

• CM, H., 2002. Generative architectural design and complexity theory. s.l.:s.n.

• Fusero P, M. L. T. A. L. S., 2013. Parametric Urbanism: A new frontier for smart cities. Planum the journal of urbanism, 27 2, pp. 1-13.

• L., C., 2008. Generation of energy-efficient architecture solutions applying GENE_ARCH: An evolution-based generative design system. Advanced Engineering Informatics, 1 Jan, pp. 59-70.

• Queiroz N, D. N. N. C. V. C., 2005. Designing a Building envelope using parametric and algorithmic processes.. CumInCAD.

• TERZIDIS, K., 2004. algorithmic design: A Paradigm Shift in Architecture?. s.l.:s.n.

• Zhang Y, L. C., 2021. Parametric Urbanism and Environment Optimization: Toward a Quality Environmental Urban Morphology. International Journal of Environmental Research and Public Health, 18 1.

In the third type, because there are some irregular changes in the depression, when facing flooding, some places will be flooded seasonally, so you can improve the quality of these spaces and ensure the utilization rate by setting seasonal parks, bike lanes, and other seasonal landscapes

• Grasshopper from street network to building geometry. Proceedings of the 2011 Symposium on Simulation for Architecture and Urban Design, 2011. 68-75.

• SPIRN, A. W. 1984. Granite garden, Basic Books.

• VAN RAVENSWAAY, C. 1991. St. Louis: an informal history of the city and its people, 1764-1865, Missouri History Museum.

• ZHANG, E., HAYS, J., TURK, G. J. I. T. O. V. & GRAPHICS, C. 2006. Interactive tensor field design and visualization on surfaces. 13, 94-107.