Transcript [Chris Wassenius]

Modeling the Interaction of Light
Between Diffuse Surfaces
Cindy M. Goral, Keenth E. Torrance, Donald P.
Greenberg and Bennett Battaile
Presented by:
Chris Wassenius
Outline
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Introduction / Motivation
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Local vs Global Illumination
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Method
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Results
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Conclusion
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Acknowledgments
Introduction / Motivation
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Accounting for global illumination is central in
producing realistic scenes.
Most surfaces reflect light diffusely back into the
environment.
Diffuse reflections of objects account for most of
the lighting in a scene.
Introduction / Motivation
Ray Tracing
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hard shadows
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ambient term needed
to simulate global
illumination
Introduction / Motivation
True Global Illumination
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soft shadows
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color bleeding
–
no need for ambient
term
Introduction / Motivation
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The proposed method, Radiosity, accounts for
indirect light surfaces.
Related Work:
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Thermal Engineering
Radiant heat exchange
Energy transport and conservation principles
Outline
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Introduction / Motivation
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Method
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Radiosity Equation
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Form Factors
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Putting It Together
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Results
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Conclusion
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Acknowledgments
Method
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Diffuse reflectors / emitters
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Enclosures
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Set of surfaces that define the illuminating
environment
Form factors
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Fraction of the radiant light energy leaving one
surface that strikes another surface
Method
Bj = radiosity of surface
j
Ej = rate of direction
emmision from
surface j
ρj = reflectivity of
surface j
Hj = incident radiant
energy arriving at
Method
What is the incident radiant energy arriving at
surface j?
This gives:
Method
Computing Form Factors
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The intensity of light reflected is constant and
uniform from all viewing directions.
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Total energy leaving a surface is found by
integrating over the hemisphere.
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Intensity of light drops proportionally with the
distance squared.
Method
Computing Form
Factors (continued)
Putting all this
together...
Method
Computing Form Factors (continued)
Identity Shortcuts
1
2
3
Method
Implementation
Step 1 - Read in polygon data
Step 2 - Subdivide polygons into patches
Step 3 - Compute form factors
Step 4 – Solve Radiosity Equation
Step 5 – Render scene
Outline
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Introduction / Motivation
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Method
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Results
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Conclusion
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Future Work
Results
Results
Results
Results
Outline
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Introduction / Motivation
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Method
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Results
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Conclusion
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Pros and Cons
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Future work
Acknowledgments
Conclusion
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Pros
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Approached realism with global illumination
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View independent solution
Cons
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Computationally expensive
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Does not account for occluded surfaces
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Does not taking into account specular reflections
Conclusions
Future Work:
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Account for occluded surfaces (hemicube method)
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Optimal polygon subdivision method
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Hierarchical storing of patches
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Faster form factor calculations