2005/06/22NCSLAB1 結合即時控制系統架構之 3D 介面 VR 系統分析 電機系控制組 (D ) 黃雋博 (R ) 彭詩淵

2005/06/22 NCSLAB 2 Outline Motivation System Architecture Technique A case study Conclusion

2005/06/22 NCSLAB 3 Motivation Interactive game environment  real time system which can interact with other people  Keeping the system maintain the display rate with 25 frame/s.

2005/06/22 NCSLAB 4 Motivation In the on-line interactive VR system, the delay will be occurred in many situations. Therefore, the timing analysis is very important for this project. The delay events that we predict are as bellow: Delay in server: Calculation time (modeling, numerical) Separate the whole environment for individual client Delay in network time: Conjunction delay Compensation Delay in client: Rendering (According to hardware of the system) Request for the server

2005/06/22 NCSLAB 5 System Architecture

2005/06/22 NCSLAB 6 Technique Control over Quality, Bandwidth, Buffer Condition, CPU’s Utilization, Scheduling Techniques for real time-systems (Ex: Rate Monotonic (RM) Algorithm, Earliest Deadline First (EDF) Algorithm)……

2005/06/22 NCSLAB 7 Technique

2005/06/22 NCSLAB 8 Technique T eb : encoder buffering delay T db : decoder buffering delay T e : encoding delay T d : decoding delay T c : networking delay T nm : numerical method computing delay T pm : physics model computing delay T v : visualization delay T eb +T db +T e +T d +T c +T nm +T pm +T v ≦ 40ms

2005/06/22 NCSLAB 9 Technique Level of Details (LOD) technique  LOD rendering techniques reduce the geometric complexity of 3D models, sacrificing visual rendering quality in order to increase frame rendering rates. Physically-based: based on physical lows or mathematical functions --- complex but real Non physically-based game : do not use physical laws--- simple but unreal  Try the best to reduce the high computational costs and maintain the reality

2005/06/22 NCSLAB 10 A case study Non-physical based method  Grassland by [Neyret 1998] translates texture to show the animated grassland  [ Neyret 1998 ]  LOD example---Grassland [Perbet and Cani 2001] highest LOD model middle LOD model lowest LOD model

2005/06/22 NCSLAB 11  Physical based models Cantilever beam model [Anjyo et al. 1992] Mass spring damped model [Miller 1988] Mass-spring model [Provot 1995] A case study

2005/06/22 NCSLAB 12 A case study  Set spring between the masses Assume the position of i th particle is the position of i+1 th particle is the internal force between the i th spring is Each particle has gravity, wind resistance and buoyancy Use Euler’s method

2005/06/22 NCSLAB 13 A case study Different types of grassNumber of masses of each grass Computatio nal time for one frame Line visualization ms Line visualization ms Spline visualization ms 1000-Grass ENVIRONMENT Bird viewLOW LOD HIGH LOD

2005/06/22 NCSLAB 14 For(i=0; i<GrassNum ; i++) { IF ( (ViewerPOS.Z- grass[i].Z)<HighLODRange) ) grass[i]  HighLODVisualization Else grass[i]  LowLODVisualization } X Y Z

2005/06/22 NCSLAB 15 A Case Study Different Types of grasslands Simulation time for one frame Line visualization (Low LOD) 15 ms Spline visualization (High LOD) 80 ms combine Line and Spline visualization 50.0 ms For Client / Sever 1000-Grass ENVIRONMENT 733MHZ Pentium III CPU Different Types of grasslands Simulation time for one frame Line visualization (Low LOD) 17.2 ms Spline visualization (High LOD) 81.3 ms combine Line and Spline visualization 34.4 ms 3GHZ Pentium IV CPU

2005/06/22 NCSLAB 16 Scheduling

2005/06/22 NCSLAB 17 Scheduling EDF

2005/06/22 NCSLAB 18 Experiment Particle: 6240 vs

2005/06/22 NCSLAB 19 Experiment - Low Quality

2005/06/22 NCSLAB 20 Experiment - High Quality

2005/06/22 NCSLAB 21 Experiment - Optimal

2005/06/22 NCSLAB 22 Conclusion The concept of LOD is used to maintain the human impression under real-time requirement. The timing analysis for real-time has been established. the rate control for large number of the VR scenario have been discussed.

2005/06/22 NCSLAB 23 References [Neyret 1998] F. Neyret, “Modeling, animating, and rendering complex scenes using volumetric textures,” IEEE Transactions on Visualization and Computer Graphics, Vol. 4, No. 1, pp. 55–70, January [Perbet and Cani 2001] Frank Perbet and Marie-Paule Cani,“Animating praires in real-time,” Proceedings of the 2001 symposium on Interactive 3D graphics, March,2001 [Anjyo et al. 1992] K. Anjyo, Y. Usami, and T. Kurihara, “A Simple Method for Extracting the Natural Beauty of Hair,” Proceedings of the 19th annual conference on Computer graphics and interactive techniques, Vol. 26, No. 2, pp , Chicago, IL, USA, July [Miller 1988] G. S. P. Miller, “The motion dynamics of snakes and worms,” Proceedings of the 15th annual conference on Computer graphics and interactive techniques, Vol. 22, No.4, pp , Atlanta, GA, USA, August 1988 [Provot 1995] X. Provot, “Deformation constraints in a mass-spring model to describe rigid cloth behavior,” Proceedings of the Graphics Interface, pp , Québec, QC, USA, May [J. Vieron and C. Guillemot 2004] J. Vieron and C. Guillemot, “Real-time constrained TCP-compatible rate control for video over the Internet,” IEEE Transactions on Multimedia, Vol. 6, Issue 4, pp , [J. Bai et al. 2002] J. Bai, Q. Liao, X. Lin, and X. Zhuang, “Rate-distortion model based rate control for real-time VBR video coding and low-delay communications,” Signal Processing: Image Communication. Vol. 17, No. 2, pp , [D. Wu et al. 2000] D. Wu, Y. T. Hou, and Y. Q. Zhang, “Transporting Real-Time Video over the Internet: Challenges and Approaches,” Proceedings of the IEEE, Vol. 88, Issue 12, pp , [B. Li and K. Nahrstedt 1999] B. Li and K. Nahrstedt, “A control-based middleware framework for quality- of-service adaptations,” IEEE Journal on Selected Areas in Communications, Vol. 17, Issue 9, pp ,1999. [C. Lu et al. 2002] C. Lu, J. A. Stankovic, G. Tao, and S. H. Son, “Feedback Control Real-Time Scheduling: Framework, Modeling, and Algorithms,” Real-Time Systems Journal, Special Issue on Control-theoretical Approaches to Real-Time Computing, 23(1/2): , July/September [Baldi and Ofek 2000] M. Baldi and Y. Ofek, “End-to-end delay analysis of videoconferencing over packet-switched networks,” IEEE/ACM Transactions on Networking, Vol. 8, Issue 4, pp , Aug. 2000