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 raytracer cannot simulate caustics adequately problems with specular daylight systems ? ? ? supplement with forward raytracer!

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)

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

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

7 The RADIANCE Photon Map Photon Map: Backward Pass View point Global photon irradiance Primary ray Ambient bounce + caustic photon irradiance

8 The RADIANCE Photon Map Photon Map: Density Estimation Find N nearest photons to x in kd-tree Irradiance E x proportional to (weighted) pho- ton density � x N r ∑ 1 Φ i E x K x x i 0 K s ds i 1 2 s 2 1 Epanechnikov kernel: K e s π r 2 r

9 The RADIANCE Photon Map Results: Compound Parabolic Concentrator

10 The RADIANCE Photon Map Results: Volume Caustics

11 The RADIANCE Photon Map Results: Y-Glass

12 The RADIANCE Photon Map Results: Lightpipe

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...

14 The RADIANCE Photon Map Conclusion Photon map enables RADIANCE to efficiently simulate caustics applicable to redirecting systems greater simulation scope ☎✝✆ Faster than RADIANCE Classic Already converged no ambient bounce / value syndrome Validation indicates adequate accuracy