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by Dietger
Wed Jul 08, 2015 2:30 pm
Forum: General Development
Topic: pbrt-v3 source code now available
Replies: 23
Views: 21474

Re: pbrt-v3 source code now available

On page 214, I don't understand the sentence "When working with these error intervals, it’s important to remember that because (1 ± em) terms represent intervals, canceling them incorrect:" Seems fine to me. Although the numerator and denominator contain the same 'term', they don't cancel...
by Dietger
Wed Nov 12, 2014 5:28 pm
Forum: General Development
Topic: Bidirectional LOD
Replies: 2
Views: 3638

Re: Light Ray Differentials

Unfortunately you cannot easily use some trivial extension of ray differentials for bidirectional level of detail. As an example, imagine some object A close to a light source. The required tessellation resolution of object A for light rays passing by should not (only) depend on their screen space f...
by Dietger
Fri Oct 03, 2014 1:26 pm
Forum: General Development
Topic: Questions about metroplis sampling.
Replies: 22
Views: 13089

Re: Questions about metroplis sampling.

Also, does anyone know how the updated metropolis sampling, which requires no warm-up, works? http://www.hungrycat.hu/MetropolisSampler.html I just looked at the code. For the most part it is just an implementation of Kelemen style metropolis with MIS but a few things stood out: 1. Instead of estim...
by Dietger
Fri Oct 03, 2014 8:46 am
Forum: General Development
Topic: Questions about metroplis sampling.
Replies: 22
Views: 13089

Re: Questions about metroplis sampling.

Does a more "difficult" path have a higher probability using MLT, while an "easy, but dark" path has a higher probability in standard path tracing? Is it possible to run both algorithms over the full path space and somehow weight the results in a way has lower error than a hard ...
by Dietger
Thu Oct 02, 2014 8:09 pm
Forum: General Development
Topic: Questions about metroplis sampling.
Replies: 22
Views: 13089

Re: Questions about metroplis sampling.

Hm. I wonder if there's some nutty MIS way to automatically combine "regular" path tracing and MLT... Well, in a way that is what Keleman is doing by mixes large step mutations with small step mutations using MIS. Basically it mixes MLT and PT using MIS. MLT is best at sampling high contr...
by Dietger
Thu Oct 02, 2014 4:10 pm
Forum: General Development
Topic: Questions about metroplis sampling.
Replies: 22
Views: 13089

Re: Questions about metroplis sampling.

...high quality samples ... On another note, whether MLT really produces higher quality samples is debatable. Sure, the sampling density is proportional to the target function, perfect importance sampling and all that, but it comes at a price. When MLT gets stuck in a peak of the target function fo...
by Dietger
Thu Oct 02, 2014 3:40 pm
Forum: General Development
Topic: Questions about metroplis sampling.
Replies: 22
Views: 13089

Re: Questions about metroplis sampling.

That way we get high quality samples AND equal amount of samples per pixel. Has anyone tried this before? You might want to look at the paper "Arbitrary Importance Functions for Metropolis Light Transport" by Hoberock. The idea is to boost the importance of dark pixels and reduce the impo...
by Dietger
Tue Jun 03, 2014 6:58 pm
Forum: General Development
Topic: VCM GPU implementation (+ some extras)
Replies: 8
Views: 6995

Re: VCM GPU implementation (+ some extras)

ad 3) The MIS used is derived for connecting to all vertices of a single "companion" path. When you connect to a subset of vertices from a superset of paths, it is possible that the optimal MIS is different. I haven't looked into it too much, but Dietger's thesis/techreport (cannot find e...
by Dietger
Fri Feb 28, 2014 10:38 am
Forum: General Development
Topic: Implementing a Shader System
Replies: 13
Views: 9247

Re: Implementing a Shader System

I don't think adding materials/shaders will slow it down much. Think again :D Unfortunately the times of 10% shading/ 90% traversal are over (if this was ever true to begin with). Traversal performance scales quite well with increased geometric complexity while shading performance does not scale al...
by Dietger
Sun Feb 23, 2014 4:04 pm
Forum: GPU
Topic: Secondary diffuse bounce much more slower
Replies: 4
Views: 4886

Re: Secondary diffuse bounce much more slower

Did you take a look at https://mediatech.aalto.fi/~timo/HPG2009/index.html ? Looking at their stats the raw ray throughput of diffuse rays is probably more like 2x/2.5x slower than raw primary ray throughput on Kepler. This is the performance of a trace-only kernel, not including any shading, but it...

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