1. Smooth View-Dependent Level-of- Detail Control and its Application to Terrain Rendering Hugues Hoppe Microsoft Research

2. Introduction To address the problem: view-dependent LOD control View-dependent progressive mesh(VDPM) In this paper, Extend the VDPM framework to provide temporal coherence through the runtime creation of geomorph

3. Introduction Implementation Which require new output-sensitive data structures. Added benefit Reducing memory used. Contribution of this paper A real-time flyover of a large,rugged terrain.

4. Introduction This paper is the first runtime scheme for view-dependent LOD control on arbitrary meshes. PS: View-Dependent Refinement of Progressive Meshes(VDPM) Hugues Hoppe(siggraph 1997)

5. Review of VDPM Framework

6. 1. The root nodes correspond to the vertices of the base mesh Mo 2. The leaf nodes correspond to the fully detailed mesh Mn

7. Review of VDPM Framework Fully Refined mesh (Mn) Selectively Refined mesh (Ms) We say that a vertex or face is active if it exists in the selectively refined mesh Ms.

8. Review of VDPM Framework Geomorph

9. Review of VDPM Framework A vsplit refinement is performed if its neighborhood satisfies 3 criteria 1. It intersects the view frustum 2. Its Gauss map is not strictly oriented away 3. Its screen-projected deviation from Mn exceeds a user-specified pixel tolerance.

10. Efficient,Temporally Smooth VDPM

11. Output-sensitive data structures Runtime generation of geomorphs

12. Efficient,Temporally Smooth VDPM Output-sensitive data structures All its data structures scale proportionally with the size n of the fully refined mesh Mn 1. Static part: Encoding the vertex hierachy and refinement dependency 2. Dynamic part: Encoding the connectivity of just the active mesh M

13. Efficient,Temporally Smooth VDPM Runtime generation of geomorphs Two factors are crucial to a good visual flythrough simulation: 1. A (high) steady frame rate 2. The absence of popping artifacts

14. Efficient,Temporally Smooth VDPM Popping occurs in an animation when successive frames show different approximate models that are visually discontinuous.

15. Efficient,Temporally Smooth VDPM Two goals (frame rate,popping) seem contradictory. To maintain a constant frame rate Adjusting the screen-space error tolerance. To eliminate popping Smoothly morphing the geometry.

16. Efficient,Temporally Smooth VDPM

17. Specialization of VDPM to Terrains

18. Exact approximation error We measure the maximum approximation error with respect to a reference surface. We therefore want to compute the maximum height deviation between this trangulated grid and the open neighborhood of each edge collapse transformation. The maximum height deviation between two triangle meshes is known to lie at a vertex of their union partition in the plane.

19. Specialization of VDPM to Terrains An efficient way to enumerate the vertices of the union partition is to consider: 1. The grid points internal to the faces adjacent to Vs 2. The grid line crossings internal to the edges adjacent to Vs

20. Specialization of VDPM to Terrains

21. Result

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