Questions tagged [importance-sampling]
The importance-sampling tag has no usage guidance.
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Lots of bad samples (below the hemisphere) when sampling the GGX VNDF
I've noticed that my implementation of GGX VNDF sampling produces quite a lot of bad samples (below the hemisphere). When such a sample occurs, I terminate the ray, leading to an immediate black pixel....
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Distance sampling with unbiased transmittance estimators
I'm currently trying some things with transmittance estimators in PBRT and I have implemented the following paper: Unbiased Ray-Marching Transmittance Estimator. This method assumes that two points $x$...
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Direct Light Sampling produces way too bright images compared to naive diffuse bounces only
it's me again! :D
I have finally implemented area lights, but without modifying the emission value of the material, this is what it looks like with indirect light only, this is what it looks like with ...
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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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Evaluating the Rendering Equation by hand (simple case)
I'm trying to make intuitive sense of the rendering equation and so I'm trying to work out a trivial example by hand, though ultimately I'm just trying to understand how monte carlo importance ...
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How does a path tracer capture light falloff if it deals exclusively with radiance?
My understanding is that path tracers deal with radiance because radiance is constant along a ray. You simply go through and evaluate the light transport equation:
$$
L_o(p, \omega_o) = L_e(p,\...
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How to approach implementing Cook-Torrence microfacet brdf?
Trying to implement the Cook-Torrance BRDF for my path tracer. Confused about how to do it though. I've seen two approaches:
1: Sample the NDF, evaluate diffuse and specular components and add them ...
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Confusion about different sampling strategies in Monte Carlo Path Tracing
I am studying Monte Carlo Path Tracing from different sources. However, I have some confusion about the sampling part and dare to post here for experts' ...
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Cosine weighted hemisphere sampling is a little bit darker and arguably noisier than reference
I'm writing a small path tracer that currently:
Samples a random light source at each bounce (direct lighting)
Bounces rays around multiple times (indirect lighting)
The scene only contains ...
- 177
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Sampling scattering direction around directions other than the last ray direction
In a path tracer, if we want to sample a ray direction in scattering medium, we can use phase function sampling, which actually use the direction of the ray before sampling as a sort of anchor to ...
- 1,112
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Questions about equi-angular sampling
Equiangular sampling is a sampling method for point (sphere) emitter in scattering medium. While it claims to be very efficient when dealing with point (sphere) emitter in scattering medium (see this ...
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Importance sampling of the blinn-phong brdf in pathtracing
tl;dr:
How do you importance sample the blinn-phong-brdf?
Recipe for importance sampling of the phong brdf as far as i understood it (pseudo-code):
...
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Confusion about the bias during Monte Carlo integration
I recently stumbled into this question:
Say, for example, we are doing mean-free-path sampling (distance sampling) in a scattering medium and to keep it simple, let's only consider the single ...
- 1,112
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Measure for volumetric rendering equation
Recently I've been digging deeper into the volumetric rendering (volumetric path tracing, to be specific). I already know that for surface rendering, there are two commonly used measures (reference ...
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How to properly use scattering coefficient during volumetric path tracing?
The increased radiance during sampling is known by:
$$
L_s = L_e + \sigma_s \int p(w, w')f_p(w, w')dw'
$$
The latter part, which accounts for in-scattering radiance bears a $\sigma_s$ in it.
The ...
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