Questions tagged [pbr]
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78
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Monte Carlo Integration
Let $I$ = the value of integration and $p$ = probability distribution.
The estimator is denoted as $\left\langle I \right >$ and is
$$\left\langle I \right >=\frac{1}{N}\sum_{i=1}^{N}\frac{f(...
- 523
6
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1
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The reciprocity of BRDF
Many books describe that a BRDF has the following property (reciprocity):
$$f_r(x, \Theta \to \Psi ) = f_r(x, \Psi \to \Theta)$$
Why is the above equation correct?
I think the above equation ...
- 523
5
votes
0
answers
140
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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(...
- 523
14
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1
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Confused with PBR implementations
I'm discovering the wonderful world of math and I'm hitting a huge wall with PBR and naming so I have a few questions:
As far as I understand BRDF describe how a material react to light (incoming ...
- 363
3
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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
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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
4
votes
1
answer
105
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How is measured BRDF data recorded?
How is measured BRDF data recorded? Like the MERL BRDF Database.
What kind of equipment is used and what are the key values that need to be recorded?
I know one place this data was used was in the ...
- 2,511
2
votes
0
answers
448
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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
12
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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 $1/(2\pi)$?
- 520
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3
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How are Physically Based Rendering Methods Researched?
Recently a question that came to my mind was that How are Physically Based Rendering Techniques researched and developed? Do people just use current equations by physicists or do they create their own?...
- 2,511
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1
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Error with tube lighting
I have recently been working on area lights for a small open source game engine called Urho3D but have run into an issues when rendering tube lights where the lights look the same as sphere lights ...
- 91
2
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1
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449
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Bug: Overly Sharp Highlights in PBR
I'm still working on my BRDF equations. Theoretically, all equations are correct, but the hilights are super sharp. I'm not sure if this is a result of me not using Image-Based Lighting (I currently ...
13
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2
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3k
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In a physically based BRDF, what vector should be used to compute the Fresnel coefficient?
The well known Schlick approximation of the Fresnel coefficient gives the equation:
$F=F_0+(1 - F_0)(1 - cos(\theta))^5$
And $cos(\theta)$ is equal to the dot product of the surface normal vector ...
- 4,420
12
votes
1
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6k
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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 ...
- 123
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3
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16bit half-float linear HDR images as (diffuse/albedo) textures?
So I been thinking about this for a while and tried to google for an answer but without any success.
If all your textures are 8bit LDR images, like JPEGs, couldn't that potentially cause conflicts ...
