課程名稱︰虛擬實境 課程性質︰選修 課程教師：歐陽明 開課學院：電資學院 開課系所︰資工所、網媒所 考試日期（年月日）︰2007.05.08 考試時限（分鐘）： 試題 : Virtual Reality Mid-term Exam, May 8, 2007 1. Augmented Reality (10%) (a) (5%) What's Augmented Reality (AR) and Mixed Reality (MR)? (b) (5%) Design an AR application. Please describe in detail about the motivation, hardware/software system, and operating scenario of your design. 2. (20%) Mr. Superplayer buys a Gundam model and uses a 3D scanner to digitize it. He wants to make an animation about Gundam, but doesn't know how to build it and let it stand on the floor. Please use OpenGL to help Mr. Superplayer. The data is given below. (a) (10%) How to combine each part to let Gundam stand? Write OpenGL code to do that. (You should define any parameters that you need, eg., "LeftLegLength" etc.) (Hint: You have glPushMatrix(), glPopMatrix(), glRoatef(), glTranslatef(), DrawBody(), DrawRightLeg(), DrawLeftLeg() etc). (b) (10%) Only three parts (Body, LeftLeg, RightLeg) are not enough for animation. By your experience, if the Gundam wants to shoot from a kneeling position, how to split the model? (PS; coordinate system is important here!) (Hint: You can simply draw "Line Segment with Label" as split part, "Circle" as joint or origin). Fig. http://i.imgur.com/Bqjt8zr.png 3. (15%) The goal of 3D sound is to simulate the direction and distance of a sound source in a real world. (a) (7%) The DVD (Digital Versatile Disk) standard uses the Dolby AC-3 as its sound output, where AC-3 uses 5 speakers plus one bass speaker, as shown in Figure 3. However, your PC has two speakers only. How would you design your PC to play a DVD movie with a sound similar to Dolby AC-3? Fig. http://i.imgur.com/ZDCT6NQ.png (b) (8%) The following is the shape of your study room, and you want to hear the music exactly as it was generated in the opera house in Paris, France. Can it be done? How? Fig. http://i.imgur.com/AgKjzQr.png 4. Term project (5%) What is the term project you want to do for this semester? What kind of technical problems will you encounter and have to be solved? 5. (5%) Please design a method to achieve the goal "smell real" in a movie theater? Give at least one example. 6. Force-feedback devices (15%) Agent Mulder build his 3D sculpting system with a force-feedback device. The pseudo code of his main algorithm is following: while(sculpting){ Do the "collusion detection" with current sculptor position Calculate the "feedback force" and set it to force-feedback device Modify the 3D scene Render the 3D scene } (a) (5%) What are the parameters that the force feedback device needs to send them back to the computer to simulate the force system? Can you write down and explain the formula for simulating the force feedback system with previous parameters? (b) (5%) Let's simulate a "rock" wall (hard surface) using such a spring system using a large spring constant K = 1000000 NT/m. Do you think it is a good system design? What are the potential problems? (c) (5%) For the problem in (b), can you think of ways to actually simulate a hard surface in virtual reality? 7. (15%) In terms of graphics acceleration, there are at least two approaches been proposed, namely (1) parallel processing or SIMD, such as in the nVidia GeForce4 chip set, and (2) binary machines such as the PixelPlanes chip set. (a) (5%) Can you describe the basic idea of how these two approaches can accelerate graphics and the major difference between them. (b) (10%) There is a functon fast_calculate (A, B, C, x, y) which can be evaluated in parallel, where fast_calculate() can calculate A*x + B*y + C for each pixel position (x, y). For a triangle defined by vertices (0, 6, 0), (0, 0, 0) and (8, 0, 0), please write a parallel procedure using fast_calculate() to draw all the pixels inside this triangle by Phong shading (vertex normal interpolation) with the shading function (surface normal) dot_product (light_direction). The surface normal at (0, 6, 0) is (1, 0, 0), at (0, 0, 0) is (0.6, 0.8, 0), and at (8, 0, 0) is (0, 1, 0), and the light is at (0, 0, 15). We view this triangle from Z axis above. 8. (15%) In order for objects in virtual environment to move realistically, the response time of the system must be very short. However, in practice, there is always system lag (latency). To solve the problem, many different methods have been proposed to "predict" the future movement upon the past motion path. One method is the simple extrapolation: Time(ms) t-200 t-100 t t+100 Input X(n-2) X(n-1) X(n) X(n+1) Value 1.2 1.3 1.5 (a) (3%) By first order linear interpolation, X(n+1) = ? (b) (5%) By second order extrapolation, X(n+1) = ? How to formulate your equation? (c) (2%)Suppose the moving object has a mass M, will this fact help the prediction? (d) (5%) Do you think more data in the past will help? Why? Is there an upper bound (number of past data) for the past data? If so, what are the factors that will limit the past length? (Hint: second order prediction: a curve passing through X(n), X(n-1), X(n-2)) --

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