课程名称︰虚拟实境 课程性质︰选修 课程教师：欧阳明 开课学院：电资学院 开课系所︰资工所、网媒所 考试日期（年月日）︰2012.05.08 考试时限（分钟）： 试题 : 2012 Virtual Reality Midterm Exam May 8, 2012 1. (20%) Hierarchical animation using OpenGL Miss Hancock buys a Luffy model and uses a 3D scanner to digitize it. She wants to make an animation about Luffy, but doesn't know how to build it and let it stand on the floor. Please use OpenGL to help Miss Hancock. The data is given below. http://i.imgur.com/2opEBFQ.png (a) How to combine each part to let Luffy stand? Please write OpenGL code to do that. You should define any parameters that you need. (ex: "LegLength") (Hint: You have glPushMatrix(), glPopMatrix(), glRoatef(), glTranslatef(), DrawBody(), DrawRightLeg(), DrawLeftLeg() etc). (b) Only three parts (Head, Body, Leg) are not enough for animation. By your experience, if Luffy wants to use rubber pistol (it means to extend his arm) to punch on his enemy as the picture to the left, 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). http://i.imgur.com/IHiszZ1.png 2. (10%) (a) Please design a method to achieve the goal "smell real" in a movie theater? Give at least one example. (b) In addition to "smell real", there is "feel real". In a fiction, there is a case showing that force feedback can be dangerous to human participants, even to the degree of being "murdered". How can this be done to a participant (user) in VR applications? Please explain. 3. (5%) Term Project: 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? 4. (20%) Rasterization (着色): Rasterization is the popular rendering technique for producing real-time 3D computer-graphics. The algorithm takes 3D scene (described as polygons) to 2D surface (usually a computer monitor). At a very basic level, rasterizers simply take a stream of vertices, transform them into corresponding 2D points on the viewer's monitor and fill in the transformed 2D triangles as appropriate. If the 3D scene is very complicated, then the number of vertices may be very large. It will take a long time to do rasterization. Consider two ways for acceleration: (a) (5%) The first method is to dynamically decrease the number of triangles passing to the rasterizer. That is, reduced a model from 10 million triangles to 10000 triangles. Can you propose one idea to achieve this goal while maintain the rendering quality from our view points? Consider the hardware acceleration using Pixel Plane, knowing that it is capable of doing the calculation Ax + By + C in parallel: (b) (10%) For a triangle defined by vertices (0, 0), (2, 4) and (6, 2) with their colors on blue channel are 10, 50, 20, respectively. Please provide the precise A, B, C values such that the result of the formula Ax + By + C indicates the value of the pixel(x,y) on the blue channel using Gouraud shading (smooth shading, or called color interpolation shading). (c) (5%) Please calculate the values of the pixels (1, 1) and (3, 2) by adopting your formula in (c). 5. (20%) 3D sound: The goal of 3D sound is to simulate the direction and distance of a sound source in a real world. http://i.imgur.com/Wkq559L.png (a) The DVD standard uses the Dolby AC-3 as its sound output, where AC-3 uses 5 speakers plus one bass speaker, as shown in Figure (a). 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? (b) Noise cancellation application. The newest version of BOSE headphones has the feature that can reduce the engine noise while in the jet airplane. Can noise cancellation be done? How? 6. (10%) Human Factors: If you are required to design an IMAX movie theater which adopts an LED screen instead of a project screen. The screen size is 11m high and 20m wide. Given that the field of view of human eye is 90 degrees in the horizontal direction and 60 degrees in the vertical direction, can you define the appropriate distance between the first row seats and the screen? Please calculate the least number of LEDs that should be used in this screen. 7. Force Display(15%) (a) (5%) Please design a system with a force feedback to simulate a case in stirring an oil tank with viscosity of 30 Newton-sec/meter, while using a Microsoft Future Force Feedback joystick with a mass of 0.3 Kg, stiffness of 0.01 Newton/meter, and viscosity of 1.17 Newton-sec/meter. Please write the necessary equations for the necessary force to be generated from the driving motors inside the joystick. (b) (10%) There exists one magic trick about the above system. When simulating a spring with stiffness of 1000 NT/m, you are holding the handle of a force feedback joystick. The harder you tense your forearm in holding the handle of the joystick, the stronger is the vibration in your hand. Can you explain this magic behavior? At what sampling frequency can this happen? (Hint: Human hand has stiffness of 400 NT/m, viscosity 5 N-sec/m, and mass 2Kg, while the joystick has a viscosity of 1.5 N-sec/m). --

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