interreflections and radiosity : the forward problem lecture #11 thanks to kavita bala, pat...
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![Page 1: Interreflections and Radiosity : The Forward Problem Lecture #11 Thanks to Kavita Bala, Pat Hanrahan, Doug James, Ledah Casburn](https://reader036.vdocument.in/reader036/viewer/2022062500/56649d4d5503460f94a2bc15/html5/thumbnails/1.jpg)
Interreflections and Radiosity :
The Forward Problem
Lecture #11
Thanks to Kavita Bala, Pat Hanrahan, Doug James, Ledah Casburn
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Cornell Box
blue huered hue
![Page 4: Interreflections and Radiosity : The Forward Problem Lecture #11 Thanks to Kavita Bala, Pat Hanrahan, Doug James, Ledah Casburn](https://reader036.vdocument.in/reader036/viewer/2022062500/56649d4d5503460f94a2bc15/html5/thumbnails/4.jpg)
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Phong Shading
•no shadows
•no object interactions
Plastic looking scene
![Page 7: Interreflections and Radiosity : The Forward Problem Lecture #11 Thanks to Kavita Bala, Pat Hanrahan, Doug James, Ledah Casburn](https://reader036.vdocument.in/reader036/viewer/2022062500/56649d4d5503460f94a2bc15/html5/thumbnails/7.jpg)
Ray Tracing
Scene doesn’t look realistic enough.
• where is the corner of room?
• is the carpet and wood supposed to be this dark?
• is window flush with wall?
![Page 8: Interreflections and Radiosity : The Forward Problem Lecture #11 Thanks to Kavita Bala, Pat Hanrahan, Doug James, Ledah Casburn](https://reader036.vdocument.in/reader036/viewer/2022062500/56649d4d5503460f94a2bc15/html5/thumbnails/8.jpg)
Radiosity – today’s topic
• carpet and wood on table is lighter
Indirect lighting affects realism.
• window has depth
• walls look more pink
• room has a corner
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The Rendering Equation – Graph Style
p p’
p’’
Visibility(shadows)
Emission(light source)
Reflectance from Surfaces
source viewer
![Page 10: Interreflections and Radiosity : The Forward Problem Lecture #11 Thanks to Kavita Bala, Pat Hanrahan, Doug James, Ledah Casburn](https://reader036.vdocument.in/reader036/viewer/2022062500/56649d4d5503460f94a2bc15/html5/thumbnails/10.jpg)
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Diffuse Interreflections - Radiosity
• Consider lambertian surfaces and sources.
• Radiance independent of viewing direction.
• Consider total power leaving per unit area of a surface.
• Can simulate soft shadows and color bleeding from diffuse surfaces.
• Used abundantly in heat transfer literature
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Irradiance, Radiosity
• Irradiance E is the power received per unit surface area
– Units: W/m2
• Radiosity – Power per unit area leaving the surface (like irradiance)
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Planar piecewise constancy assumption
•Subdivide scene intosmall “uniform” polygons
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N
jjieii jiFi
1
)(:
Power Equation
• Power from each polygon:
•Linear System of Equations:
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i jA A
xyxy
yx
j
dAdAyxVrA
ijF ),(coscos1
)(2
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Form Factors Invariant
i jA A
xyxy
yx
j
dAdAyxVrA
ijF ),(coscos1
)(2
ji AijFAjiF )()(
j iA A
yxxy
yx
i
dAdAyxVrA
jiF ),(coscos1
)(2
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Form Factor Computation
•Schroeder and Hanrahan derived an analytic expression for polygonal surfaces.
•In general, computing double integral is hard.
•Use Monte Carlo Integration.
i jA A
yyxy
yx
j
dAdAyxVrA
ijF ),(coscos1
)(2
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Form Factor Computation
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Form Factor Computation
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Linear System of Radiosity Equations
KnownKnown
Unknown
• Matrix Inversion to Solve for Radiosities.
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Doug James
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Wireframe
![Page 26: Interreflections and Radiosity : The Forward Problem Lecture #11 Thanks to Kavita Bala, Pat Hanrahan, Doug James, Ledah Casburn](https://reader036.vdocument.in/reader036/viewer/2022062500/56649d4d5503460f94a2bc15/html5/thumbnails/26.jpg)
•ClassicalApproach
•NoInterpolation
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Wireframe
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•ClassicalApproach
•Low Res
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•ClassicalApproach
•High Res
•More accurate
![Page 30: Interreflections and Radiosity : The Forward Problem Lecture #11 Thanks to Kavita Bala, Pat Hanrahan, Doug James, Ledah Casburn](https://reader036.vdocument.in/reader036/viewer/2022062500/56649d4d5503460f94a2bc15/html5/thumbnails/30.jpg)
•ClassicalApproach
•High Res
•Interpolated
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Sample Scenes
![Page 33: Interreflections and Radiosity : The Forward Problem Lecture #11 Thanks to Kavita Bala, Pat Hanrahan, Doug James, Ledah Casburn](https://reader036.vdocument.in/reader036/viewer/2022062500/56649d4d5503460f94a2bc15/html5/thumbnails/33.jpg)
Sample Scenes
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Sample Scenes
![Page 35: Interreflections and Radiosity : The Forward Problem Lecture #11 Thanks to Kavita Bala, Pat Hanrahan, Doug James, Ledah Casburn](https://reader036.vdocument.in/reader036/viewer/2022062500/56649d4d5503460f94a2bc15/html5/thumbnails/35.jpg)
Sample Scenes
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Sample Scenes
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Summary
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Doug James
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Two Pass Solution
• First Pass: Diffuse Interreflections
View independent, global diffuse illuminationcomputed with radiosity.
• Second Pass: Specular Interreflections
View dependent, global specular illuminationcomputed with ray-tracing.
• Combine strengths of radiosity and ray-tracing.
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Interreflections :
The Inverse Problem
Lecture #12