Questions tagged [pathtracing]
For questions about the path tracing Monte Carlo algorithm for physically accurate global illumination, or its variants.
246 questions
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How do you derive the integral equation of transfer in the PBRT book?
In the PBRT book section on the equation of transfer, they give the equation
$\frac{\partial}{\partial t}L_o(p',\omega) = -\sigma_t(p',\omega)L_i(p',-\omega)+\sigma_t(p',\omega)L_s(p',\omega)$,
and ...
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Normal Map causing uneven lighting in PathTracer
I have been working on a Path Tracer ~ following the Peter Shirley Series
I decided to add "normal map" feature to the same, Normal Map Tutorial is the tutorial I followed. But the output I ...
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How does PBRT rewrite the majorant transmittance integral over segments when sampling the majorant transmittance?
In the PBRT book section on Sampling the Majorant Transmittance, they take the equation:
$\int_0^t \sigma_{maj}(p')T_{maj}(p \to p')f(p')dt'$,
and using the multiplicative property of transmittance
$...
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Optimizing the direction field in the volume rendering integral — literature pointers?
I am looking for works in the volume-rendering / radiative-transport literature that treats the direction $\hat{\omega}(x)$ as an optimizable function rather than a known input function. That is, one ...
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How is this null-scattering transmittance equation in PBRT derived?
In the PBRT book section on null scattering, they define the null-scattering coefficient $\sigma_n$ and the constant majorant $\sigma_{maj}$, and define the equation:
$\frac{dL_o(p, \omega)}{dt} = -(\...
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Issue with derivation of the Volterra integral formulation of volumetric transmittance on pbr-book.org
In the fourth edition of Physically Based Rendering, they take equation 11.9:
$\int_0^d \frac{dL(p + t\omega)}{dt} \, dt = L(p') - L(p) = \int_0^d -\sigma_t(p + t\omega) \, L(p + t\omega) \, dt$,
and ...
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Handling probabilities with Spectral "Null Tracking"
I have confused myself to the point where i dont know what up or down are. I will try to keep things focused, but certain decisions may need a paragraph of motivation.
For some time now me and a ...
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Problem with geometric term in bidirectional path tracer
I'm trying to implement a bidirectional path tracer, and I'm currently facing a problem when related with the Geometric term (at least that is what I think).
My work as been mostly based in the beach ...
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Convergence of Microfacet BRDF vs Primitive BRDFs
I have been implementing a path tracer - while I initially started the process using a dummy Lambertian diffuse BRDF to focus on the base path tracer, I recently added a microfacet BRDF as an option. ...
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Is MIS needed to sample different types of lights with RIS?
I'm looking into sampling different types of lights using RIS, namely spheres and env maps. But I'm wondering if, since all the proposal samples in "regular" RIS come from one proposal ...
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Monte Carlo integration of the Path Space integral
In Eric Veach's thesis, chapter 8.2.2, he says that:
Our goal is to estimate the path integral:
$$I_j = \int_{\Omega}f_j(\overline x) d\mu(\overline x)$$
for each measurement $I_j$. To do this, the ...
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Explicit Light Sampling: Where does $n \cdot l$ come from?
In these lecture notes: http://www.cs.utoronto.ca/~strider/docs/D18_DistributionRayTracing.pdf on page number 140 (as labelled on the PDF), it says that if we perform explicit light sampling, the ...
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Wavelength to RGB conversion issue. Average RGB result is yellow tinted instead of white
I'm currently implementing dispersion in my RGB path tracer.
How I do things:
When I hit a glass object, sample a wavelength uniformly between 360nm and 830nm and assign that wavelength to the ray
...
- 301
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Emmanuel Turquin's energy compensation method for thin walled glass is losing energy. Theoretically speaking, how can that happen?
I'm using Turquin's method to compensate for energy losses in my BSDFs. I'm currently working on thin walled glass (with a microfacet distribution, this is not just pure specular thin glass).
The idea ...
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One-sample multiple importance sampling, with environment and brdf
I am writing a pathtracer, and I want to somehow incorporate importance sampling of the environment map. The obvious way to do this seems to use MIS to either importance sample from my material bsdf ...
