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

visualization and graphics research group CIPIC January 21, 2003Multiresolution (ECS 289L) - Winter 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

visualization and graphics research group CIPIC January 21, 2003Multiresolution (ECS 289L) - Winter 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

visualization and graphics research group CIPIC January 21, 2003Multiresolution (ECS 289L) - Winter 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

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

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

visualization and graphics research group CIPIC January 21, 2003Multiresolution (ECS 289L) - Winter 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

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

visualization and graphics research group CIPIC January 21, 2003Multiresolution (ECS 289L) - Winter 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

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

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

visualization and graphics research group CIPIC January 21, 2003Multiresolution (ECS 289L) - Winter 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)

visualization and graphics research group CIPIC January 21, 2003Multiresolution (ECS 289L) - Winter Outside Reading H. Hoppe. Progressive Meshes. Computer Graphics Proceedings, Annual Conference Series, ACM SIGGRAPH, 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