Questions tagged [pbr]
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78
questions
2
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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 ...
- 53
1
vote
1
answer
247
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Confusion over Microfacet-based BRDFs and Normal Distribution Functions
Through reading various sources online, I've become a bit confused. I'll briefly outline what I think I do understand:
My understanding is that microfacet-based BRDFs assume there is always a perfect ...
- 229
3
votes
1
answer
208
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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{\...
CommunityBot
- 1
0
votes
0
answers
63
views
Unable to compute fresnel reflections properly
I am implementing fresnel reflections for materials in my renderer.
According to this source, here the look I should obtain when rendering a sphere over a grey background:
I have two implementations. ...
- 103
0
votes
1
answer
168
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Does fresnel reflection make sense for metals?
I am implementing fresnel reflections for materials in my renderer.
Does it make sense for metals?
Here my implementation:
...
- 2,222
0
votes
0
answers
179
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One-sample model Multiple Importance Sampling with balance heuristic
Recently I feel a bit confused about one-sample model MIS. One sample model MIS can be found here in Veach 1997. 9.2.4 The one-sample model, and this one-sample model is widely used in the opensource ...
- 1,112
1
vote
1
answer
101
views
Shading normal and geometric normal for refractive surface rendering
I got confused when implementing my own renderer. I read this from the PBR-book:
Fortunately, there is an elegant solution to these problems. When evaluating the BSDF, we can use the geometric normal ...
- 1,112
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.
...
- 41
12
votes
2
answers
3k
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Why normalise Lambertian BRDF by 1/pi?
Why is a Lambertian BRDF normalised by dividing by $\pi$? Since the area of a unit sphere is $4 \pi$, and the area of the half sphere above the surface is $2 \pi$, shouldn't it rather be $1/(2\pi)$?
- 36
18
votes
2
answers
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What is the accepted method of converting shininess to roughness, and vice versa?
Most modern renderers use physically-based materials and their models are often parameterized over roughness. Since this wasn't always the case with renderers, conventional assets often don't have a ...
CommunityBot
- 1
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votes
1
answer
127
views
how can I compute a roughness map without any 3D softwares?
Recently, I want to use a roughness map to get better rendering results.
Most information on the internet is about the operation of 3D software.
So, how can I generate a roughness map of my own 3D ...
CommunityBot
- 1
1
vote
1
answer
175
views
The purpose of NdotV in the directional-hemispherical reflectance equation in the book "Real-time rendering book"
I have been reading the book "real-time rendering 4th edition" and came across this Directional-hemispherical reflectance equation.
$$R(\mathbf{l}) = \int_{\mathbf{v}\in\Omega} f(\mathbf{l}, ...
4
votes
3
answers
451
views
Texture prefiltering for Linearly Transformed Cosines
I'm implementing Real-Time Polygonal-Light Shading with Linearly Transformed Cosines from Siggraph 2016.
I'm stuck on the texture prefiltering (section 5.3).
As I understand they use ...
0
votes
1
answer
322
views
BRDF for point lights should not return values over 1
This is standard Cook-Torrance BRDF in formulation for a single point light. No intergrals over a hemisphere, just a single direction to a source of incoming energy.
$$
L_o = { \bigg ( (1-F) \frac{...
CommunityBot
- 1
1
vote
1
answer
66
views
Is the dichromatic model physically based?
lately I have been learning about photometry, and everywhere I look I see a BRDF written according to the "dichromatic model". Roughly speaking: $$\rho= \rho_D+\rho_S \cdot (...)$$
for some $...
- 25.1k