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）︰2014.05.11 考试时限（分钟）： 试题 : Virtual Reality Midterm Exam(Make-up) May 11, 2014 1. (15%) da Vinci Surgical System The da Vinci System is designed to facilitate complex surgery using a minimally invasive approach. It consists of a surgeon's console that is typically in the same room as the patient, and a patient-side cart with four interactive robotic arms controlled from the console. Please answer the following questions: http://i.imgur.com/4Zp38no.png (a.) (10%) What technologies related to Virtual Reality are involved in this system? Please list 3 items and give a brief explanation. (b.) (5%) How can the surgeon know that the robotic arms had touched the patient? What good things will you design to inform the surgeon about the above situation? 2. 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? 3. (25%) In terms of graphics acceleration, there are at least two approaches been proposed, namely (1) parallel processing or SIMD, such as in the nVidia GeForce chip set, and (2) binary machines such as the PixelPlanes chip set. (a) (10%) There is a functon fast_calculate (A, B, C, x, y) which can be evaluated in parallel, where fast_calculate() can calculate Ax + By + C for each pixel position (x, y) in PixelPlanes. For a triangle defined by vertices (1, 2), (4, 4) and (7, 0), please write a parallel procedure using fast_calculate() to draw all the pixels inside this triangle. (b) (10%) For the triangle defined by vertices (1, 2), (4, 4) and (7, 0) with their colors on blue channel are 17, 31, 21, 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 color values of the pixels (4, 3) and (5, 2) by adopting your formula in (b). 4. (10%) Motion Capture Motion capture is the process of recording the movement of objects or people. Traditionally, the captured subject would wear several markers and the related motion would be recorded by several surrounding cameras. Nowadays, Kinect uses depth cameras to track human skeleton motion. Hint: Kinect's depth acquisition is enabled by "light coding" technology. The process codes the scene with near-IR light, light that returns distorted pattern depending upon where things are. The solution then uses a standard off-the-shelf CMOS image sensor to read the coded light back from the scene using various algorithms to triangulate and extract the 3D data. (a) (5%) Compare the traditional maker method and Kinect system. What are the pros and cons of each method? (b) (5%) Assume that you can capture human skeleton motion successfully. Please give one example of the possible cool usage, especially those that are not yet mentioned in the Internet introduction. 5. (20%)Tracking problem. From one camera, you are looking at a triangle with known vertex positions, such as A(1, 3, 10), B(8, 30, 10), C(20, 2, 10). (a) (10%) How to determine the distance and orientation of the camera to the triangle? (b) (10%) In actual use, there are cases when one vertex of the triangle is blocked from the camera's view. What would be possible solutions to this problem? Please state your solution clearly and with explanation. 6. (10%) In Windows 8, a multi-touch screen similar to Apple's I-phone is one unique way to provide new user interfaces. Assume that we have "two" cameras in each Notebook PC, located at the top right and left corner of the screen. (a) (5%) Can you describe a way to provide "multi-touch" user interfaces without even "touching" the screen? (b) (5%) Please describe your algorithm to solve the problem of determining finger positions (not just one, but perhaps two fingers). 7. (10%) 3D sound: The goal of 3D sound is to simulate the direction and distance of a sound source in a real world (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? http://i.imgur.com/Wkq559L.png 8. Force-feedback devices (15%) Allen builds his 3D sculpting system with a force-feedback device. The pseudo code of his main algorithm is given in the following: ┌────────────────────────────────────┐ │while(sculpting){ │ │ Do the "collision detection" with current sculptor position │ │ Calculate the "feedback force" and send it to force-feedback device │ │ Modify the 3D scene │ │ Render the 3D scene │ │} │ └────────────────────────────────────┘ Assuming the joystick stiffness = 0, mass = 0.5 KG, and viscosity = 4 NT-Sec/Meter, While human operator (arm and wrist) stiffness = 400 NT/m, viscosity = 3 NT-Sec/Meter, and mass = 3 kg. (a) (5%) Let's simulate a spring (with spring constant K = 100) with a length of 50 cm, while at both ends are "rock" walls (hard surface) using such a spring system using a large spring constant K = 1000000 NT/m. Your joystick is at the middle of the spring, say at 25 cm. Please write down your simulation equations. (b) (5%) Do you think it is a good system design? What are the potential problems? Hint: (for a system to be stable: Sampling period T <= B/K, where B is the total system viscosity, K is the total system stiffness.) (c) (5%) For the problem in (b), can you think of ways to actually simulate a hard surface in virtual reality, and still feels "realistically"? --

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