Questions tagged [physically-based]
The physically-based tag has no usage guidance.
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Point light source radiance
I was reading Deriving radiance from irradiance and intensity and the last comment said that by dividing $r^2$ we convert radiant intensity to irradiance. What confuses me then is the fact that for ...
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Why is the indirect illumination (using IBL) in my PBR shader overpowering everything?
I'm trying to implement a basic form of physically based rendering (PBR) and I am using the PBR tutorial from learnopengl dot com as a reference.
The PBR I am implementing consists of two parts, ...
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Understanding the BRDF Equation
I am studying the BRDF equation. From Wikipedia, the equation is as follows:
I have one main question:
Where does the $\cos{\theta_i}$ in the denominator come from?
The denominator implies that $...
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Narrow-phase CCD in FEM topology query (finite element method)
I am implementing IPC from siggraph2020, and one of its step is about CCD line search, where CCD is applied each iteration in the descent method in a part of the algorithm.
I have implemented CCD ...
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Term confusion about volume scattering
We have two different terms, for example, let's talk about scattering only.
Scattering coefficient
Scattering cross-section
These two terms are supposed to have different physical meaning. I read it ...
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Rendering equation integration variable change
I'm watching the TU Wien rendering lectures in the course we were presented with a rendering equation (first one on the screenshot) and then another, which results from a change of variables (if I ...
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Difficulty in understanding the interpretation of propagation of an exitant function from the book Advanced Global Illumination (2nd ed)
The book defines operator $\mathcal{T}$ for the propagation of an exitant function as:
if I'm assuming that the position of the point $x$ is on the top-left surface, and that $\Psi$ is considered as ...
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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 ...
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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 $...
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Diffuse irradiance map : confusion about photometric vs radiometric units
I have spent the longest amount of time just taking the terminology for granted & have only just recently started studying or at least trying to understand the difference between radiometric and ...
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Cosine in Rendering Equation and BRDF cancel out: Why cosine at all?
I am somewhat confused with the following issue reading about the rendering equation and BRDFs. That is, the BRDF is usually defined as surface radiance $Lr(ω_r)$ over irradiance $L_i(ω_i)cosθ_i$ for ...
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How is the beam transmittance calculated in PBRT V3?
In pbrt v3, the book gives this description of beam transmittance, but I don't know how to solve the differential equation like it says to get Tr , can someone please tell me how to solve the ...
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What's The Math Behind This Cloth Animation?
I progammed a simple cloth animation. Initially I tried to implement Hooke's law, but it wasn't numerically stable, presumably because I used explicit Euler. Anyway, I came up with something (WebGL2 ...
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Rendering Hypercentric Perspective
I came across some Non-Euclidean Games which involve Hyperbolic Spaces, Spherical Spaces, Portals, etc. And, I noticed that they give quite deep feel of what Non-Euclidean Spaces feel like. So, I was ...
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Motivation behind tesselation
This question is NOT about the hardware difficulties and shortcomings of tesselation shaders
I am trying to understand the motivation behind tesselation shaders.
Why/when/where tesselation is a good ...
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