Skip to main content

Questions tagged [monte-carlo]

Algorithms generating large sets of random numbers to simulate real-world, usually optical systems.

19 questions with no upvoted or accepted answers
Filter by
Sorted by
Tagged with
3 votes
0 answers
42 views

Is this way of transforming QMC samples into barycentric tri coordinates agnostic to mesh-topology?

While I'll try my best to give all relevant info in all possible brevity below, please refer to the spoiler and link at the bottom of the post for the (more lengthy) original description if needed. ...
Herbert Jensch's user avatar
3 votes
0 answers
221 views

Understanding BRDF sampling

I'm trying to understand BRDF importance sampling following the exemples of the lambertian/diffuse model and the reciprocal Phong model. I would like to be able to extend the principle to other ...
kipgon's user avatar
  • 151
3 votes
0 answers
565 views

Problem with specular BRDF (Monte Carlo & Path Tracing)

Above on the left is my attempt and on the right is what I'm aiming for.As you can see my sphere with the specular brdf has a weird dark ring In my radiance function I am recursing through the ...
Aloof's user avatar
  • 31
2 votes
0 answers
89 views

Implementing monte carlo path traced refractions problem

I am writing a forward monte carlo path tracer with the added feature of specular refractions for transparent materials, I have managed to come this far but something is not quite right and I am ...
Marcus's user avatar
  • 21
2 votes
0 answers
164 views

Scaling of the final image in Metropolis Light Transport

I don't understand why the PBR implementation of Metorpolis Light Transport scales the final image by b / mutationsPerPixel. The authors write: Each Metropolis ...
0xbadf00d's user avatar
  • 203
2 votes
0 answers
100 views

Quantify the variance of pixel measurements

Say $E_j$ is an estimator of the value $$I_j=\int f_j\:{\rm d}\lambda$$ of the $j$th pixel given by the path space integral of the corresponding measurement contribution function $f_j$. $f_j$ is of ...
0xbadf00d's user avatar
  • 203
2 votes
0 answers
54 views

Chart swaps and path inversion in bidirectional path tracing

I've got a hard time to understand how we would implement the following in practice. I'd be great if someone could explain the details for the example below. Assume we're generating a path ${\rm x}=(\...
0xbadf00d's user avatar
  • 203
2 votes
0 answers
602 views

What's the nature of Monte Carlo noise?

Monte Carlo rendering is just a process of sampling and reconstruction to evaluate the rendering equation. Why is it called noise rather than error?
chaosink's user avatar
  • 591
2 votes
0 answers
161 views

Picking multiple light sources from a mixture densities

According to Peter Shirely paper, one pdf(probability density function) can be defined for the union of the light sources and pick only one using a random number from this density: $$p(x) = \alpha_1 ...
ali's user avatar
  • 740
1 vote
0 answers
79 views

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' ...
bim's user avatar
  • 135
1 vote
0 answers
71 views

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 ...
Enigmatisms's user avatar
1 vote
0 answers
167 views

Applying Monte-Carlo methods in path tracing

I've noticed that I consistently get worse results in path-tracing when I try to do monte-carlo correctly compared to when I don't, and I think this might be because of a fundamental misunderstanding. ...
Kate's user avatar
  • 11
1 vote
0 answers
36 views

Report standard deviation in Rendering results

I noticed that a common metrics for image quality assessment (Monte Carlo path tracing) is MSE between the generated image and a reference one. My question is: why isn't the standard deviation ever ...
maurock's user avatar
  • 189
1 vote
0 answers
145 views

Tail Recursive Monte Carlo Raytracing

I am writing a raytracer in F# using montecarlo sampling I would like to make my recursive calls tail recursive but I am not sure of this is possible with MC raytracing as one has to evaluate sampled ...
Marc HPunkt's user avatar
1 vote
0 answers
79 views

Sample Correlation and Random Variables -- An Intuitive Explanation?

I'm mainly trying to understand what it means for Monte Carlo samples to be correlated. Can somebody fit this into the theory of what I know about random variables, covariance and correlation? And ...
demonFudgePies's user avatar
0 votes
0 answers
197 views

Visualize the variance of an image

Let $h_j$ denote the image reconstruction filter of pixel $j$. I'm estimating the color value $$I_j=\int h_jf\:{\rm d}\mu$$ of the $j$th pixel (see [Veach, Section 8.2]) by an asymptotically ...
0xbadf00d's user avatar
  • 203
0 votes
0 answers
94 views

Relation between camera sensor responsivity and image reconstruction filter associated with a pixel

Let $W_{\text e}$ denote the camera sensor responsivity (i.e. importance) and $h_j$ and $W_{\text e}^{(j)}$ denote the image reconstruction filter and sensor response associated with the $j$th pixel, ...
0xbadf00d's user avatar
  • 203
0 votes
0 answers
53 views

Distribution of the first vertex on a camera subpath in bidirectional path tracing

Suppose we are sampling camera rays of a perspective camera with a finite aperture. The PBRT implementation of the sampling scheme looks like this: ...
0xbadf00d's user avatar
  • 203
0 votes
0 answers
211 views

Multiple Importance Sampling in Bidirectional Path Tracing

I'm trying to understand the computation of the path density described in the book Physically Based Rendering. They assume that a path $$x=(x_0,\ldots,x_{n-1})=(q_0,\ldots,q_{s-1},p_{t-1},\ldots,p_0)$$...
0xbadf00d's user avatar
  • 203