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Questions tagged [microfacet]

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3
votes
0answers
71 views

Microfacet GGX not integrating as expected

I'm trying to complete a look-up table for an energy-conserving variation of microfacet GGX as implemented here: https://patapom.com/blog/BRDF/MSBRDFEnergyCompensation/ I have a (pretty standard) GGX ...
3
votes
1answer
97 views

Can microfacet BRDF (including ggx) represent perfect mirror?

Perfect mirror's brdf is simple, $F\frac{\delta(\omega_i-\omega_r)}{|\cos(\theta_r)|}$ as in http://www.pbr-book.org/3ed-2018/Reflection_Models/Specular_Reflection_and_Transmission.html As shown in ...
1
vote
1answer
109 views

Why can I see the diffuse lighting effect on a perfect mirror?

Currently I am learning PBR by Unity3D. I find that even I turn the smoothness to 1, I can still see the diffuse lighting effect, which does not make any sense to me. Imagine I trace a ray from my ...
1
vote
1answer
155 views

Can't understand the Importance sampling GGX

I've read many articles relating to importance sampling of GGX. However, I still feel confused. The formula of GGX is : And many article says we should use this formula to sample: In the formula, ...
5
votes
0answers
45 views

Ask for help on understanding a formula related to change of variable

Although I have tried for a long time, I cannot understand Eq.(11) of paper "Microfacet Models for Refraction through Rough Surfaces" written by Bruce Walter, Stephen Marschner, Hongsong Li and ...
4
votes
0answers
261 views

Wrong output while implementing GGX importance sampling

I'm receiving a non-energy conserving output while trying to importance sample the GGX Distributionof the Microfacet model, which is generally 3-4 times bigger than the resulting PDF I'm following ...
3
votes
2answers
268 views

Relationship between roughness and BRDF

In a BRDF $f_r$, assume Cook-Torrance model, we have a microfacets distribution $D$. This distribution essentially models the rougheness of the material as far as I've understood. Given a direction $v$...
9
votes
1answer
3k views

Correct form of the GGX geometry term

I'm trying to implement a microfacet BRDF in my raytracer but I'm running into some issues. A lot of the papers and articles I've read define the partial geometry term as a function of the view and ...
11
votes
1answer
535 views

Compensation for energy loss in single-scattering microfacet BSDF models

Single-scattering microfacet-based surface models like the original Torrance-Sparrow BRDF or derived models like the BSDF for rough dielectric surfaces by Walter et al. neglect inter-reflection of ...
8
votes
1answer
361 views

How does Smith multiple scattering interact with diffuse subsurface scattering?

The Multiple Scattering Microfacet BSDFs with the Smith Model paper describes a statistical model for replacing the masking-shadowing functions in microfacet BSDFs (which account for paths with more ...