epilectrolytics wrote: ↑
Mon Jul 08, 2019 6:11 pm
http://www.jp.square-enix.com/tech/libr ... ctions.pdf
This is a solution for GDG-paths (glossy-diffuse-glossy) in BiDir, still not a solution for SDS-paths, but it works for glossiness at 0.0001 which means it solves the SDS problem when we use no mirrors but metals and glasses with just a tiny bit of roughness.
Very interesting paper. Thank you for the link. I think the authors assume good approaches for generic improvements of ray tracing, Bidirectional reflectance Distribution function (BRDF).
Following short view of the paper content for people interested in this topic.
Hierarchical Russian Roulette for Vertex Connections
YUSUKE TOKUYOSHI, SQUARE ENIX CO., LTD., Japan TAKAHIRO HARADA, Advanced Micro Devices, Inc., USA
Our contributions are as follows.
• To accelerate a huge number of Russian roulette operations for vertex connections, we propose a hierarchical rejection algorithm using a stochastic scattering range from an eye vertex.
light vertex eye vertex
• For this hierarchical rejection, we introduce a top-down ran- dom number assignment method to decorrelate variance.
• We also introduce an SEL approximation to represent the
scattering range with a tight ellipsoid for anisotropic glossy reflections.
9 CONCLUSIONS (summarized)
+an acceleration technique for a huge number of Russian roulette operations for connections between an eye vertex and many cached light vertices.
+a different random number for each Russian roulette operation
+an efficient hierarchical random number assignment algorithm
+random numbers only for visited nodes.
+a squared ellipsoidal lobe function to approximate an anisotropic scattering lobe created by the microfacet BRDF.
+is easy to integrate into BPT-based algorithms without changing the heuristic of multiple importance sampling.
+improves the ro- bustness for specular-diffuse-glossy or glossy-diffuse-glossy paths
+works efficiently for extremely glossy reflections that are hard to distinguish from perfectly specular reflections
-technique does not support perfectly specular surfaces“
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