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HCI - DM 6121: Assignment 2 (Direct Manipulation and Multi-touch Interaction) Name: Toe Kyaw Kyar Student ID: G0902359G Email: toek0001@e.ntu.edu.sg

PART 1: Direct Manipulation Principles Three Principle of Direct Manipulation The object in the computer and the action performed on this object must be visible continuously while performing this physical action. The result or impact of this undoable and incremental physical operation must also be visible immediately and rapidly. No complex command language syntax must be used. It should make the user to interact with the graphical objects in computer. Advantages of Direct Manipulation Less error and make the user know the status of action he/she performed continuously. Easy to learn and understand for the all users ranged from novices to experts. Fast and encourage exploration and give the user satisfaction. Potential Problems of Direct Manipulation May be difficult and take more time to program. May be some problem is designing and modifying interaction device such as small display device. Metaphors can lead misleading as the user doesn’t care the essence behind the metaphors.

PART 2: Multi-Touch Interaction Mainly used hardware technologies for sensing multiple finger actions are: Capacitive Sensing Technology and Optical Imaging Technology Capacitance Based Tech: Developed based on capacitive coupling effect to detect position. The insulator screen coated with a transparent conductor. As the finger is a conductor, touching the surface make the body’s electrostatic field a little bit changed which can be


measured as a change in capacitance. There are many technologies to determine the position of the touch. Some are mutual capacitance method_ using grids and self capacitance method_ using sensing circuits and electrodes. Pros: It can work faster. The screen can be cleaned by cloths as it sense only conductive materials. Touching with non conductive things avoid command input. Cons: It is more expensive to manufacture. A stylus cannot be used for this screen and for this reason handwritten cannot be implemented. Camera Based Tech: Developed based on infra-red rays scattered off from touching the screen. The projectors project the image through an acrylic screen onto the surface facing the viewer. When the user touches, the infra-red light from LEDs scattered off and this rays are captured by the infra-red camera of reflection sensors. Software generated motion and position of touch based on the information gathered from sensors. Pros: Ease of use. User can use your finger or stylus to interact with the device. It can recognize handwriting or sketch on the screen. More robust. Cons: It is expensive. Mostly not portable as its size is relatively big. Advantages of Using Multi-Touch Interaction Some actions such as resize, drag and some others action can be implemented in a natural way than the single touch interaction system. It is easy to handle & control the screen. Problems of Using Multi-touch Interaction If the user uses his/ her fingers for a few minute, there may be stress on their finger tips. There is the problem of finger prints on the screen surface. There may be ghost touch problem when more than one touches.

PART 3: Survey on the Multi-touch Interactions Supported in Microsoft Surface™ In the Microsoft Surface™ System, there are four capabilities that make it unique. These are: Direct Interaction Multi-touch Functionality Multi-user Functionality Object Recognition The Microsoft Surface™ experience responds to touch and direct manipulation, whether by one finger, many fingers, or physical objects. The actions become temporal and unmediated


in the way that content is manipulated naturally. The main functionalities that support direct manipulation are direct interaction and multi-touch functionality. And all the objects and actions on these objects are made visible. Its direct manipulation capability can be seen easily. For example, users can explore a music library by flipping through album covers, or play a chess game by using physical game pieces. And also in the application Microsoft Surface Lagoon, the user can interact and manipulate directly with the system. User can play with water and make the fishes swim away by just touching the screen with one or more finger. User can attract fishes by touching and holding easily. In this example, the user sees objects and can input the action upon objects by multi-touch functionality. And also user can know and see the completion of the action or operation performed on objects. Pros: It is quick and easy to handle touch surface. It encourages exploration. Multi-touch interface allows more functions and users. Innovative design and user experience. Large surface area to view multiple windows and objects. Object recognition: increased functionality helping the user in speed and ease of use. The touch material needs not be conductive as this product uses the optical imaging technology. Cons: It is really expensive product. It would allow only a limited number of businesses to posses it. It is not convenient if it is the special purpose computer. There needed many application software to run on it. To be able to develop many applications, the prices must be dropped. (suggestion) Need for dim lighting. No Audio inputs. (must be able to work in every environment and must have audio input: suggestion) Need to put specially designed bar codes_ Surface Tags or RFIDs on the objects for the system to recognize. It is not portable and quite inconvenient because of its size. This makes it harder for people to transport from one place to another. (I think, no way to solve.) If one table is shared by 4 people, privacy becomes an important issue. So the issue of personal space must be clearly arranged. (suggestion) Accuracy may becomes problem when the user point with the fat finger. Reaching across the table can cause the arm to stiff. No optical disk drives such as DVDs, Blue Rays. (Must have: suggestion) The application must face the one who launch the application. It is more convenient that user can change the orientation of the application appeared. (suggestion)


Direct Maipulation and Multi-touch Interaction