Modeling the Interaction of Light Between Diffuse Surfaces Cindy M. Goral, Keenth E. Torrance,...
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Transcript of Modeling the Interaction of Light Between Diffuse Surfaces Cindy M. Goral, Keenth E. Torrance,...
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
● Introduction / Motivation– Local vs Global Illumination
● Method● Results● Conclusion● Acknowledgments
Introduction / Motivation
● 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– hard shadows – ambient term needed
to simulate global illumination
Introduction / Motivation
True Global Illumination– soft shadows– color bleeding– no need for ambient
term
Introduction / Motivation
● The proposed method, Radiosity, accounts for indirect light surfaces.
● Related Work:– Thermal Engineering
Radiant heat exchange
Energy transport and conservation principles
Outline
● Introduction / Motivation ● Method
– Radiosity Equation– Form Factors– Putting It Together
● Results● Conclusion● Acknowledgments
Method
● Diffuse reflectors / emitters● Enclosures
– Set of surfaces that define the illuminating environment
● Form factors– 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 surface j
Method
What is the incident radiant energy arriving at surface j?
This gives:
Method
Computing Form Factors– The intensity of light reflected is constant and
uniform from all viewing directions.– Total energy leaving a surface is found by
integrating over the hemisphere.– 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
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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
● Introduction / Motivation ● Method● Results● Conclusion● Future Work
Results
Results
Results
Results
Outline
● Introduction / Motivation ● Method● Results● Conclusion
– Pros and Cons– Future work
● Acknowledgments
Conclusion
● Pros– Approached realism with global illumination– View independent solution
● Cons– Computationally expensive– Does not account for occluded surfaces– Does not taking into account specular reflections
Conclusions
Future Work:– Account for occluded surfaces (hemicube method)– Optimal polygon subdivision method– Hierarchical storing of patches– Faster form factor calculations