Search found 50 matches
- Wed Jul 08, 2015 2:30 pm
- Forum: General Development
- Topic: pbrt-v3 source code now available
- Replies: 23
- Views: 25137
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 because t...
- Wed Nov 12, 2014 5:28 pm
- Forum: General Development
- Topic: Bidirectional LOD
- Replies: 2
- Views: 4204
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...
- Fri Oct 03, 2014 1:26 pm
- Forum: General Development
- Topic: Questions about metroplis sampling.
- Replies: 22
- Views: 15595
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...
- Fri Oct 03, 2014 8:46 am
- Forum: General Development
- Topic: Questions about metroplis sampling.
- Replies: 22
- Views: 15595
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 partitioning? Yes, t...
- Thu Oct 02, 2014 8:09 pm
- Forum: General Development
- Topic: Questions about metroplis sampling.
- Replies: 22
- Views: 15595
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 contribution pa...
- Thu Oct 02, 2014 4:10 pm
- Forum: General Development
- Topic: Questions about metroplis sampling.
- Replies: 22
- Views: 15595
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...
- Thu Oct 02, 2014 3:40 pm
- Forum: General Development
- Topic: Questions about metroplis sampling.
- Replies: 22
- Views: 15595
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 importance of ...
- Tue Jun 03, 2014 6:58 pm
- Forum: General Development
- Topic: VCM GPU implementation (+ some extras)
- Replies: 8
- Views: 8454
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 either righ...
- Fri Feb 28, 2014 10:38 am
- Forum: General Development
- Topic: Implementing a Shader System
- Replies: 13
- Views: 10655
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...
- Sun Feb 23, 2014 4:04 pm
- Forum: General Development
- Topic: Secondary diffuse bounce much more slower
- Replies: 4
- Views: 5846
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...