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Rendering Transitions in a Geometric Level of Detail Framework
Defended by Shaun David Ramsey
On July 27, 2004
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Outline
Motivation - Hierarchy of Structure Contributions
Arbitrary Polyhedral Simplification Structure Combination Ray Tracing Techniques
Results
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Video Generation
Large amount of detail dependent on viewing angle, and viewing location
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Rendering Structure
Macro Meso Micro
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Geometry
Mesh Sizes continue to grow Varied Representations
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Simplification
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Level of Detail Hierarchies
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Progressive Meshes
Level Of Detail Hierarchy Edge Collapse Texture Mapping
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What’s Missing?
Mesostructure Displacement maps Bump maps
Microstructure BRDFs
Algorithms to utilize Rendering Methods
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What’s Missing? BRDFs
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What’s Missing? Bump Maps
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What’s Missing? Displacement Maps
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What’s Missing? Rendering Transitions
Construct BRDFs, bump maps and displacement maps with consistent intensities
Redistributed bump mapping algorithm
Becker and Max 1993
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Spanning the Gap
Combine simplifications for meso-, micro- and macrostructure
Incorporate view-dependent rendering techniques in a geometric level of detail framework.
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Outline
Motivation - Hierarchy of Structure
Contributions Arbitrary Polyhedral Simplification Structure Combination Ray Tracing Techniques
Results
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Arbitrary Polyhedral Simplification
Edge collapses for arbitrary polyhedra Ramsey, Bertram, and Hansen [CGIM 2003]
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Normal Deviation
Use normal deviation to drive simplification Complicated records for APS
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Changing Thresholds
Original Simplified Simplified21590 polys 5600 polys 5600 polys
cos=0.95 cos=0.0
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Outline
Motivation - Hierarchy of Structure Contributions
Arbitrary Polyhedral Simplification Structure Combination (Rendering+LOD) Ray Tracing Techniques (BPs, Disp PMs)
Results
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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)
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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)
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Construct Normal Distributions
Ray Trace displaced plane with scalar height field (why not use bilinear patches)
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Bilinear Patches
Eliminate Bias
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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)
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Quadratics
Reduce numerical error and instability
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Efficiency
790m intersection tests Ray-Bilinear Patches 754s (1.05m tests/s) Two Plane-Bilinear Patches 963s (0.82m tests/s)
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Ray Traced PMs with Rendering Transitions
General Algorithm with Discrete LOD Determine LOD Li to use (d)
Ray Trace Li
Determine Rendering Method (d, ) If Displaced or Partial Bump, ray trace
Else compute intensity from BRDF and RBM
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Negative Displacements
d
-d
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Transitioned Displacements
Partial bumps with negative displacements
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Ray Tracing Displacements
Many levels of 4-to-1 subdivision Pass proportion to each triangle
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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
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Outline
Motivation - Hierarchy of Structure Contributions
Arbitrary Polyhedral Simplification Structure Combination Ray Tracing Techniques
Results
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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
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Results - transitions
Disp are greenBumps are blueBRDFs are red
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Results – changing LOD
4500 polys 3500 polys 3500 polys 2500 polys
2500 polys 1500 polys 1500 polys 500 polys
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Results – user params
Change transitions, change PMs, heights
Disp are green Bumps are blue BRDFs are red
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Results - Movies
Displaced Movie - Scintillation Color Movie – when transitions are used Rendered Movie – the full LOD/transition
system
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Rendering Times
Rendering Method
Mesh 0.33s 0.11s 0.38s
BRDF 0.40s 0.11s 0.45s
RBM 3.70s 1.40s 3.99s
Displaced Detailed 24.95s 5.09s 41.52s
LOD Transition System 3.70s 1.33s 31.28s
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Future Work
Shadows Displacement map rendering Distributed Ray Tracing
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Other Rendering Techniques
Realistic Materials Subsurface scattering BRDFs (anisotropy, specularity)
Replace the BRDF with Bitextures Hardware (VDMs)
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The End
•Questions?