Dynamic Parallax Occlusion Mapping with Approximate Soft Shadows

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Dynamic Parallax Occlusion Mapping with
Approximate Soft Shadows

• Natalya Tatarchuk
• I3D 2006
• Presented by ???

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Outline

• Introduction
• Related Work
• Parallax Occlusion Mapping (POM)
• Height Field-Ray Intersection
• Soft Shadows
• Result
• Conclusion

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Introduction -1

• Motivation
• Creating a realistic scene without rendering a
  complex geometry.
• Earlier Work
• Bump Mapping Blinn 1978
• Displacement Mapping Cook 1984

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Introduction -2

• Displacement Mapping
• In ray-tracing based approach
• High computational costs
• Adapt poorly to programmable GPU
• In image-warping techniques
• Perspective-correct geometry
• Require precomputed visibility data
• Large memory footprint
• Hard to integrate into GPU pipeline

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Introduction -3

• Inverse Displacement Mapping
• Take advantage from novel GPU pixel pipeline
• Lack of correct object silhouettes
• Accurate silhouettes can generated by using
  view-dependent displacement data
• In this paper
• Present a significant improvement in rendering
  quality for production level results

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Introduction -4

• Contributions in this paper
• High precision computation algorithm for critical
  height field-ray intersection
• Real-time computation of soft shadows due to
  object self-occlusions
• Adaptive LOD control system for controlling
  shader complexity

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Related Work -1

• Horizon mapping technique Max 1988
• Allows shadowing bump map using precomputed
  visibility maps
• Inexpensive
• Excessive surface flattening at grazing angles
• Precomputed 3D distance map Donnelly 2005
• Create 3D distance map for rendering
• Texture fetches latency -gt not applicable

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Related Work -2

• Relief Mapping Policarpo et al. 2005
• Mapping relief data in tangent space for
  per-pixel displacement mapping
• Take excellent advantage form GPU
• Generate dynamic lighting with self-occlusion,
  shadows, motion parallax
• Strong aliasing and excessive flattening at steep
  viewing angles

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Related Work -3

• LOD control systems
• A LOD system for bump mapped surfaces Fournier
  92
• Automatic shader simplification which uses
  controllable parameters Olano et al. 2003
• Distance
• Size
• Importance
• Given hardware limits

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POM Height FieldRay Intersection -1

• Determine the intersection point C
• Linear search
• Binary search

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POM Height FieldRay Intersection -2

• Simply using a linear search
• Requires higher precision for the root-finding
• More samples for higher-frequency high field
• Sample size controlled by artists or automatic
  controlled by a linear function

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POM Height FieldRay Intersection -3
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POM Soft Shadows -1

• Substituting the Lts for the Vts, cast ray again
• Compare the intersection of the point with the
  original displaced point
• Generates hard shadows which can display aliasing
  artifacts in some scenes

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POM Soft Shadows -2

• Sample n samples h1 hn along the light
  direction ray

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POM Soft Shadows -3

• Heuristically approximate the size of penumbra
  for the occluded pixel
• Compute the blocker-to-receiver ratio

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POM Soft Shadows -4

• Compute penumbra coefficient
• Scaling the contribution of each sample by
  distance of the sample from h0
• Using the maximum value sampled
• Apply during lighting computation
• Compute soft shadows only for areas which are
  actually facing the light source

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POM Soft Shadows -4

• Relief Map Parallax Occlusion Map

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POM Adaptive LOD Control SYS

• Provide a rendering optimization and smooth
  transition
• Lowest LOD is rendered using bump mapping
• Determine mip level and compare with threshold
• Expose the threshold to the artists

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Result -1 (Compare with original model)
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Result -2 (LOD SYS)
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Result -3(Comapre with Bump Map - LOD 0)
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Result -4(Compare with Relief Map)
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Conclusion

• DEMO ToyShop
• Contribution
• Limitation
• Lack of detailed silhouettes
• Provide a high level of directability to the
  artist
• Improve visual quality over the previous
  approaches