rendering transitions in a geometric level of detail framework

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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?