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Rendering Transitions in a Geometric Level of Detail Framework

Rendering Transitions in a Geometric Level of Detail Framework. Defended by Shaun David Ramsey On July 27, 2004. Outline. Motivation - Hierarchy of Structure Contributions Arbitrary Polyhedral Simplification Structure Combination Ray Tracing Techniques Results. Video Generation.

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Rendering Transitions in a Geometric Level of Detail Framework

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  1. Rendering Transitions in a Geometric Level of Detail Framework Defended by Shaun David Ramsey On July 27, 2004

  2. Outline • Motivation - Hierarchy of Structure • Contributions • Arbitrary Polyhedral Simplification • Structure Combination • Ray Tracing Techniques • Results

  3. Video Generation • Large amount of detail dependent on viewing angle, and viewing location

  4. Rendering Structure Macro Meso Micro

  5. Geometry • Mesh Sizes continue to grow • Varied Representations

  6. Simplification

  7. Level of Detail Hierarchies

  8. Progressive Meshes • Level Of Detail Hierarchy • Edge Collapse • Texture Mapping

  9. What’s Missing? • Mesostructure • Displacement maps • Bump maps • Microstructure • BRDFs • Algorithms to utilize Rendering Methods

  10. What’s Missing? BRDFs

  11. What’s Missing? Bump Maps

  12. What’s Missing? Displacement Maps

  13. What’s Missing? Rendering Transitions • Construct BRDFs, bump maps and displacement maps with consistent intensities • Redistributed bump mapping algorithm Becker and Max 1993

  14. Spanning the Gap • Combine simplifications for meso-, micro- and macrostructure • Incorporate view-dependent rendering techniques in a geometric level of detail framework.

  15. Outline • Motivation - Hierarchy of Structure • Contributions • Arbitrary Polyhedral Simplification • Structure Combination • Ray Tracing Techniques • Results

  16. Arbitrary Polyhedral Simplification • Edge collapses for arbitrary polyhedra • Ramsey, Bertram, and Hansen [CGIM 2003]

  17. Normal Deviation • Use normal deviation to drive simplification • Complicated records for APS

  18. Changing Thresholds Original Simplified Simplified 21590 polys 5600 polys 5600 polys cos=0.95 cos=0.0

  19. Outline • Motivation - Hierarchy of Structure • Contributions • Arbitrary Polyhedral Simplification • Structure Combination (Rendering+LOD) • Ray Tracing Techniques (BPs, Disp PMs) • Results

  20. Structure Combination • Rendering System required to glue pieces together • Ray Tracing Bilinear Patches for Normal Distributions (BRDFs, RBM) • Ray Tracing Displaced Progressive Meshes (Combines LOD with Appearance)

  21. Rendering Transitions • Becker [1992] and Becker and Max [1993] • Construct BRDFs and RBMs from normal distributions • Transition between BRDFs, RBMs (interpolation) and between RBMs and displacement maps (partial bumps)

  22. Construct Normal Distributions • Ray Trace displaced plane with scalar height field (why not use bilinear patches)

  23. Bilinear Patches • Eliminate Bias

  24. Ray Tracing Bilinear Patches • Bilinear Patches [Ramsey, Potter, Hansen JGT 2004] • P(t) = r + t q • P(u,v) = (1-u)(1-v) p00 + (1-u)v p01 + u(1-v) p10 + uv p11 = a uv + b u + c v + d • Solve P(u,v) = P(t)

  25. Quadratics • Reduce numerical error and instability

  26. Efficiency • 790m intersection tests • Ray-Bilinear Patches 754s (1.05m tests/s) • Two Plane-Bilinear Patches 963s (0.82m tests/s)

  27. Ray Traced PMs with Rendering Transitions • General Algorithm with Discrete LOD • Determine LOD Lito use (d) • Ray Trace Li • Determine Rendering Method (d, q) • If Displaced or Partial Bump, ray trace Else compute intensity from BRDF and RBM

  28. Negative Displacements d -d

  29. Transitioned Displacements • Partial bumps with negative displacements

  30. Ray Tracing Displacements • Many levels of 4-to-1 subdivision • Pass proportion to each triangle

  31. Contributions • Arbitrary Polyhedral Simplification • Rendering (Ray Tracing): • Bilinear Patch Intersections • Displaced Progressive Meshes • Rendering Transitions • Combining Rendering Transitions in a Geometric Level of Detail Framework

  32. Outline • Motivation - Hierarchy of Structure • Contributions • Arbitrary Polyhedral Simplification • Structure Combination • Ray Tracing Techniques • Results

  33. Effect of Subdivision Level l=1, *4 l=2, *16 l=3, *64 l=4,*256 l=5, *1024 l describes subdivision level, * describes triangles rendered per original triangle in the model

  34. Results - transitions Disp are greenBumps are blue BRDFs are red

  35. Results – changing LOD 4500 polys 3500 polys 3500 polys 2500 polys 2500 polys 1500 polys 1500 polys 500 polys

  36. Results – user params • Change transitions, change PMs, heights Disp are green Bumps are blue BRDFs are red

  37. Results - Movies • Displaced Movie - Scintillation • Color Movie – when transitions are used • Rendered Movie – the full LOD/transition system

  38. Rendering Times

  39. Future Work • Shadows • Displacement map rendering • Distributed Ray Tracing

  40. Other Rendering Techniques • Realistic Materials • Subsurface scattering • BRDFs (anisotropy, specularity) • Replace the BRDF with Bitextures • Hardware (VDMs)

  41. The End • Questions?

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