1. visualization and graphics research group CIPIC January 21, 2003Multiresolution (ECS 289L) - Winter 20031 Dynamic View-Dependent Simplification for Polygonal Models By Julie C. Xia and Amitabh Varshney Presented by Jaya Sreevalsan Nair and Christopher Co

2. visualization and graphics research group CIPIC January 21, 2003Multiresolution (ECS 289L) - Winter 20032 Introduction Problem: Meshes too large AND Simplified mesh not necessarily visually accurate Desire: Visual accuracy of fine meshes with the efficiency of coarse representation Image from Xia96

3. visualization and graphics research group CIPIC January 21, 2003Multiresolution (ECS 289L) - Winter 20033 Previous Work (1/2) Level-of-Detail (LOD) Representations for Mesh Simplification –Statically generated Vertex deletion (Schroeder et al),Vertex collapse (Rossignac and Borrel), Edge collapse (Hoppe et al), Wavelet Decomposition (Gross et al), etc. Curvature-guided simplification, proposed by Hamann and Turk Change in tolerance volume (Gueziec) –Dynamically generated Progressive Meshes (Hoppe) –( M 0, { split 0, split 1, split 2, … split k-1 } ) –selective refinement –Continuous LOD

4. visualization and graphics research group CIPIC January 21, 2003Multiresolution (ECS 289L) - Winter 20034 Previous Work (2/2) Issues not addressed by Progressive Mesh Representation –Non-optimal series of edge collapses (distance metric driven) –Linear time complexity for accessing node –No efficient updating of frame- to-frame selective refinements

5. visualization and graphics research group CIPIC January 21, 2003Multiresolution (ECS 289L) - Winter 20035 Guidelines for Image-Space Simplification Local Illumination Screen-Space Projections Visibility Culling Silhouette boundaries

6. visualization and graphics research group CIPIC January 21, 2003Multiresolution (ECS 289L) - Winter 20036 Overview of the Method Hierarchy Construction –Preprocessing –Static Hierarchy Traversal –Run time –Dynamic

7. visualization and graphics research group CIPIC January 21, 2003Multiresolution (ECS 289L) - Winter 20037 Construction Merge tree (binary tree) –Edge collapse –Parent – child relationships –Euclidean distance stored (“upswitch” and “downswitch”) Region of Influence Termination –User specified minimum number of vertices –No more legal edge collapses Dependencies

8. visualization and graphics research group CIPIC January 21, 2003Multiresolution (ECS 289L) - Winter 20038 Example for dependencies Image from Xia96

9. visualization and graphics research group CIPIC January 21, 2003Multiresolution (ECS 289L) - Winter 20039 Traversal Choosing display vertices –Check Upswitch / Downswitch distances T > U : Vertex marked “inactive” for display T < D : More refinement needed –Check dependencies To select final list of display vertices –Frame-to-frame coherence Display vertex list for the next frame Choosing display triangles –Interleaved with display vertex selection Immediate deletion and addition of triangles

10. visualization and graphics research group CIPIC January 21, 2003Multiresolution (ECS 289L) - Winter 200310 Results(1/2) Image from Xia96

11. visualization and graphics research group CIPIC January 21, 2003Multiresolution (ECS 289L) - Winter 200311 Results(2/2) Image from Xia96

12. visualization and graphics research group CIPIC January 21, 2003Multiresolution (ECS 289L) - Winter 200312 Conclusion (Pros vs. Cons) Contribution Data structure (merge tree) for efficient mesh update for continuous LOD representation Advantages Continuous LOD Incremental update between frames Avoids illegal edge collapses efficiently Logarithmic vertex lookup Disadvantages What should T be? In core Storage overhead (linear)

13. visualization and graphics research group CIPIC January 21, 2003Multiresolution (ECS 289L) - Winter 200313 Outside Reading H. Hoppe. Progressive Meshes. Computer Graphics Proceedings, Annual Conference Series, ACM SIGGRAPH, 1996. J. Xia, J. El-Sana, and A. Varshney. Adaptive Real-Time Level- of-detail-based Rendering for Polygonal Models. IEEE Transactions on Visualization and Computer Graphics. Vol. 3, No. 2, June 1997, pp 171 - 183