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The RADIANCE Photon Map Roland Schregle Fraunhofer Institute for - - PowerPoint PPT Presentation
The RADIANCE Photon Map Roland Schregle Fraunhofer Institute for - - PowerPoint PPT Presentation
The RADIANCE Photon Map Roland Schregle Fraunhofer Institute for Solar Energy Systems Freiburg, Germany 2 The RADIANCE Photon Map Motivation: Caustics 3 The RADIANCE Photon Map Motivation: Backward Raytracing RADIANCE is a backward
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3 The RADIANCE Photon Map
Motivation: Backward Raytracing
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RADIANCE is a backward raytracer cannot simulate caustics adequately problems with specular daylight systems supplement with forward raytracer!
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4 The RADIANCE Photon Map
Photon Map (Wann Jensen, 1995)
Forward raytracer Monte Carlo (light) particle transport simulation Two pass method Couples to RADIANCE’s ambient calculation (backward pass)
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5 The RADIANCE Photon Map
Photon Map: Forward Pass
Photons emitted from light sources Scattered / absorbed at surfaces Indirect hits stored in space subdividing data structure (kd-tree) Photon attributes: flux Φ, position x, normal N
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6 The RADIANCE Photon Map
Photon Map: Forward Pass
Three photon types: Global: (diffuse specular) diffuse illumina- tion Caustic: specular diffuse illumination Volume: global inscattering in mist
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7 The RADIANCE Photon Map
Photon Map: Backward Pass
Ambient bounce + caustic photon irradiance Primary ray View point irradiance Global photon
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8 The RADIANCE Photon Map
Photon Map: Density Estimation
xFind N nearest photons to x in kd-tree Irradiance E x proportional to (weighted) pho- ton density
E x
N
∑
i 1
K x xi Φi
r 0 K s ds
1
Epanechnikov kernel: Ke s
2 πr2 1 s r
2
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9 The RADIANCE Photon Map
Results: Compound Parabolic Concentrator
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10 The RADIANCE Photon Map
Results: Volume Caustics
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11 The RADIANCE Photon Map
Results: Y-Glass
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12 The RADIANCE Photon Map
Results: Lightpipe
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13 The RADIANCE Photon Map
Validation
How does photon map measure up to theory and RealLife
✁✄✂? Analytical validation using simple geometry accurate within 0.5% Experimental validation using test box with illu- minance sensors in progress...
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