Questions tagged [microfacet]
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26 questions
0 votes
0 answers
43 views
Convergence of Microfacet BRDF vs Primitive BRDFs
I have been implementing a path tracer - while I initially started the process using a dummy Lambertian diffuse BRDF to focus on the base path tracer, I recently added a microfacet BRDF as an option. ...
3 votes
1 answer
336 views
Lots of bad samples (below the hemisphere) when sampling the GGX VNDF
I've noticed that my implementation of GGX VNDF sampling produces quite a lot of bad samples (below the hemisphere). When such a sample occurs, I terminate the ray, leading to an immediate black pixel....
- 301
0 votes
1 answer
2k views
What does GGX stand for?
Many render engines implement the microfacet model for rendering surfaces that are rough, metallic, and/or transparent, a concept first published in "A Reflectance Model for Computer Graphics&...
1 vote
1 answer
109 views
How is the distribution of normals constructed from the distribution of slopes in 'Understanding the masking-shadowing function' paper?
Recently I'm reading Eric Heitz's paper 'Understanding the Masking-Shadowing Function in Microfacet-Based BRDFs', in section 5, 5.2, the paper defines the distribution of slopes and then says the ...
- 69
1 vote
1 answer
217 views
Conflicting definitions for the distribution of normals $D$ in microfacet BSDFs
Please do not confuse this question with this one. In Understanding the Masking-Shadowing Function in Microfacet-Based BRDFs, Eric Heitz defines the distribution of normals as. There, the footnote. ...
3 votes
1 answer
257 views
Confusion of deriving the Jacobian of the reflection transformation in Walter et. al's 2007 paper
When deriving the Jacobian of the reflection transformation in Walter et. al's 2007 paper: First we have a macrosurface BSDF which is: $f_{s}(\mathbf{i}, \mathbf{o}, \mathbf{n})=\int\left|\frac{\...
- 31
1 vote
0 answers
93 views
Implementing the derivation of the Smith Shadowing function for arbitrary distributions
I'm trying to implement the derivation of the masking function G_1 by Smith. The appendix of Walter et al 1, Hammons presentation 2 and this research paper 3 talk in detail about it and I feel as I do ...
- 41
0 votes
1 answer
170 views
Microfacet BRDF artifacts
I've been trying to implement a microfacet specular BRDF based on the equations in Real Shading in UE4, but I'm getting weird ring-shaped artifacts in the highlights of rough surfaces: Here's the ...
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