Questions tagged [pbr]
The pbr tag has no usage guidance.
23
questions with no upvoted or accepted answers
5
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answers
140
views
What is the potential equation in PBR?
I'am studying PBR and the book introduce the potential equation.
They said the potential equation can describe shooting algorithms better, and
$W(x, \theta)$ describes the fraction of the radiance $L(...
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4
votes
0
answers
2k
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Explanation of math of the Smith G1 term
In appendix A of the paper Microfacet Models for Refraction through Rough Surfaces there is a derivation provided for $\Lambda(w)$ but the mathematics is very confusing. Could somebody help me by ...
- 2,511
3
votes
0
answers
653
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Comparing different sampling methods for GGX IBL
I have made a demo that shades a sphere with an environment map. I wanted to compare 3 different ways of sampling the environment.
Uniform sampling.
Importance sampling with the NDF as suggested in ...
- 137
3
votes
0
answers
81
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Predicting reflectance functions from complex surfaces
There are three principal ways to obtain a BRDF. We can
Derive an analytic formula using physical principles
Use simulation given an assumed or measured model of the surface
microgeometry
Measure the ...
- 2,511
3
votes
0
answers
521
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Mathematics of Sub Surface Scattering
Can somebody help explain the mathematics of Sub Surface Scattering in a Path Tracer based on the Diffuse Approximation in A Practical Model for Subsurface Light Transport ?
I would like someone to ...
- 2,511
2
votes
0
answers
129
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"Charlie" Sheen BRDF's directional albedo integrates to values higher than 1 at low roughnesses. Does this mean it is not energy conserving?
I am implementing the BRDF from the 2017 paper "Production Friendly Microfacet Sheen BRDF". This BRDF is modelled as a coat layer stacked on top of a base specular. In order to do so in an ...
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2
votes
0
answers
164
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Scaling of the final image in Metropolis Light Transport
I don't understand why the PBR implementation of Metorpolis Light Transport scales the final image by b / mutationsPerPixel.
The authors write:
Each Metropolis ...
- 203
2
votes
0
answers
106
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How are fluid simulations handled in Computer Graphics?
How are fluid simulations handled in Computer Graphics? For a novice, there are hardly any novice friendly tutorials explaining how particles or fluids can be simulated.
Things like smoke, crown ...
- 2,511
2
votes
0
answers
448
views
Is there a material table for the Cook Torrance BRDF?
Is there a material table that lists all the specific values to obtain a certain type of material (e.g: copper or asphalt) available?
I found this table in the paper: A Reflectance Model for ...
- 2,511
1
vote
0
answers
69
views
replace IBL with single color - the lighting equation
I want to avoid IBL (image based lighting), however my scenes are way too dark - especially close-to-mirror like surfaces, which get little contributions from other direct light sources in the scene.
...
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1
vote
0
answers
94
views
Why my bsdf can not pass Chi2test?
I implemented a MicrofacetTransmission in nori. But it can not pass all Chi2test when alpha is large(>= 0.4 or ?),part of chi2test is passed.And I can not found the problem.Can someone help me?
...
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1
vote
0
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136
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Contour-line looking artifact on diffuse irradiance map
I tried implementing my own diffuse irradiance map maker after reading Learn OpenGL > PBR > IBL > Diffuse Irradiance.
It takes an HDR image and makes six HDR cube map.
But It keeps making ...
- 111
1
vote
0
answers
70
views
How to handle negative reflection directions in raytracing?
I got a function that generates samples from a GGX visible normal distribution function. When I use it to calculate reflection directions obviously some of these intersect with the surface agin (...
- 11
1
vote
0
answers
84
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Questions about BRDF parameterization
Hi I'm trying to get a better understanding of the BRDF modeling. I only implemented naive diffuse(lambert), specular and microfacet BRDF before, but I don't have much experience in mixed BRDFs and ...
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1
vote
0
answers
880
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GGX BRDF is greater than 1?
I am implementing a GGX BRDF, this is the formula I used is from:https://schuttejoe.github.io/post/ggximportancesamplingpart1/
And this is my implementation:
...
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