Precomputed Global Illumination of Isosurfaces

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Precomputed Global Illumination of Isosurfaces

• Masters Defense
• Kevin BeasonDavid C. Banks, Advisor

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Computer Graphics

Sphere position 1 0 0
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Visualization
Image
Data
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Scalar Field
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Level Sets
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Example Level Sets
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Rendering
Photon Mapping
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Thesis Statement

• Level sets can be displayed in real time with
  high quality graphics

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Is this new?
Local Illumination
Global Illumination
Fast (hw)
X
NEW
Slow(sw)
X
X
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Local vs. Global Illumination
Local
Global
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Rendering Equation
Global
Local
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Perceptual Cues
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Boat wake
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Boat wake
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Image Credits

• Neuron - Blanco, Ouimet, Banks, Beason
• Vislab - Yagi, Banks, Beason
• Boatwake - Sussman, Banks, Beason
• Atrium - Dabrovic, Beason

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Global Illumination of Isosurfaces

• Global Illumination is good
• How do I apply it to isosurfaces quickly?
• Precompute GI for all level sets Lc
• Save solutions

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How?

• Naïve approach
• Extract a level set
• Illuminate it (wait)
• Save illumination
• Repeat for every isovalue c
• Retrieve at runtime

amira
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Example heightfield
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Scalar Field
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Level sets

• Lc (x,y) h(x,y) c

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Raised Level Sets

• (x, y, h(x,y)) h(x,y) c

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Flat Light in D
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Flat Light in DxR
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Flat Light on Graph
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Physical Example
2D Analytic Heightfield Function
plaster
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Flattened Light
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Raising water level
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Sum of Level Sets Illumination
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Mathematical Model

• Flattened Light Transport
• 2D case

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Duality

• Two isosurfaces
• Same light

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Ordinary Light
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Flattened Light
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Flat 3D Rend. Eqn.

• Requires modification of Emission and Reflection

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Flat 4D Rend Eqn.

• Behaves just like ordinary 3D light
• Operates it in raised leaf of R4

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Ordinary vs. Flattened
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Sample Illumination on Graph
Samples are taken uniformly in Domain (R3)
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Interpolate into 3D Texture

• Use Shepard Interpolation
• Or Tent Filter

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Apply Texture

• Use Marching Squares to extract Level Set
• Use texture-mapping to apply 3D texture

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Results

• Movies
• Amira

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Thank You

• Brad Futch, Josh Grant, Wilfredo Blanco (amira
  network), Hui Song
• Dr. Ouimet, Dr. Hussaini, Dr. Piekarewicz, Dr.
  Smith (Datasets)
• Dr. Liu, Dr. Sussman (Committee)
• Dr. Banks (Advisor)