結合即時控制系統架構之 3D 介面 VR 系統分析

1. 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 (D92921003)黃雋博 (R93921067)彭詩淵 NCSLAB

2. Outline • Motivation • System Architecture • Technique • A case study • Conclusion 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. 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 NCSLAB

5. System Architecture 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)…… NCSLAB

7. Technique NCSLAB

8. Technique • Teb: encoder buffering delay • Tdb: decoder buffering delay • Te: encoding delay • Td: decoding delay • Tc: networking delay • Tnm: numerical method computing delay • Tpm: physics model computing delay • Tv: visualization delay • Teb+Tdb+Te+Td+Tc+Tnm+Tpm+Tv≦40ms NCSLAB

9. 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 Technique NCSLAB

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

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

13. LOW LOD Bird view HIGH LOD A case study 1000-Grass ENVIRONMENT NCSLAB

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

15. A Case Study For Client / Sever 733MHZ Pentium III CPU 1000-Grass ENVIRONMENT 3GHZ Pentium IV CPU NCSLAB

16. Scheduling NCSLAB

17. Scheduling • EDF NCSLAB

18. Experiment • Particle: 6240 vs. 14040 NCSLAB

19. Experiment - Low Quality NCSLAB

20. Experiment - High Quality NCSLAB

21. Experiment - Optimal 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. 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 1998. • [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. 111-120, Chicago, IL, USA, July 1992. • [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. 169-178, 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. 147-154, Québec, QC, USA, May 1995. • [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. 634-646, 2004. • [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. 187-199, 2002. • [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. 1855-1877, 2000. • [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. 1632-1650,1999. • [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): 85-126, July/September 2002. • [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. 479-492, Aug. 2000 NCSLAB