Search found 97 matches

by ypoissant
Tue Jun 24, 2014 11:19 pm
Forum: General Development
Topic: Energy-Conserving Phong Specular Lobe
Replies: 10
Views: 8517

Re: Energy-Conserving Phong Specular Lobe

The energy conservation scene you describe will work for Lambertian BRDF. But for a Phong based BRDF, because radiance is not reflected uniformly, the plane will 'appear' darker or brighter depending on the camera position and the Phong exponent. That is normal. Can you clarify what you mean by thi...
by ypoissant
Fri Jun 20, 2014 10:29 pm
Forum: General Development
Topic: Energy-Conserving Phong Specular Lobe
Replies: 10
Views: 8517

Re: Energy-Conserving Phong Specular Lobe

I am trying to get correct Phong specular for a simple path tracer. The test scene is a plane with no diffuse but a specular component. Above the plane is a dome emitting light <0.5,0.5,0.5>, with no reflection at all. The camera is inside the dome. The dome appears gray and, since every ray bounci...
by ypoissant
Fri Jun 13, 2014 12:44 am
Forum: General Development
Topic: Color space: when to multiply by the matrix
Replies: 13
Views: 9187

Re: Color space: when to multiply by the matrix

as long as there is no fluorescence, incomplete linear color spaces can be used (such as sRGB), but what about fluorescence ? Couldn't this cause out-of-gammut colors to appear ? Probably yes. But aren't gammuts only of concern for an input and output devices? What matter does it make if the calcul...
by ypoissant
Wed Jun 11, 2014 11:11 pm
Forum: General Development
Topic: Color space: when to multiply by the matrix
Replies: 13
Views: 9187

Re: Color space: when to multiply by the matrix

My impression is that it is better to render in a color space that is as close to the input color spaces as possible and then transform to the final output color space. I don't see any improvements that can be gained in term of render precision in transforming the input color space into some rendere...
by ypoissant
Mon Apr 07, 2014 12:27 pm
Forum: General Development
Topic: Measure the convergence speed
Replies: 20
Views: 14237

Re: Measure the convergence speed

Dade: My tile size is 8x8. I use the max error of 2x2 pixels.

I'm going to read the other papers too. Thanks Tarlak.
by ypoissant
Mon Apr 07, 2014 3:04 am
Forum: General Development
Topic: Measure the convergence speed
Replies: 20
Views: 14237

Re: Measure the convergence speed

The two are equivalent, other than a constant scale factor (All = Odd/2 + Even/2 => All - Even = Odd/2 - Even/2). If the firefly comes from a single even-numbered sample, then it should be twice as bright in the even image, since there are half as many total samples. Perhaps you were taking the dif...
by ypoissant
Sun Apr 06, 2014 8:53 pm
Forum: General Development
Topic: Measure the convergence speed
Replies: 20
Views: 14237

Re: Measure the convergence speed

Recently, I did some work on this topic and based on some of the papers listed in this thread. I'm very happy of the results. Following your post, I also implemented the algorithm as outlined in "Progressive Path Tracing with Lightweight Local Error Estimation". However, I found that using (AllSamp...
by ypoissant
Fri Mar 28, 2014 6:42 pm
Forum: General Development
Topic: Microfacet (RoughGlass) and Multiple Importance Sampling
Replies: 13
Views: 9640

Re: Microfacet (RoughGlass) and Multiple Importance Sampling

I had a discussion about Walter et al BTDF here on ompf a few months ago. You might find the thread interesting.
viewtopic.php?f=3&t=1807
And I, too, had difficulties implementing it. In the end, I just abandoned.
by ypoissant
Tue Mar 25, 2014 6:56 pm
Forum: General Development
Topic: Microfacet (RoughGlass) and Multiple Importance Sampling
Replies: 13
Views: 9640

Re: Microfacet (RoughGlass) and Multiple Importance Sampling

And also the paper by Walter et al "Microfacet Models for Refraction through Rough Surfaces"
https://www.cs.cornell.edu/~srm/publica ... -btdf.html

Since you are doing refraction through microfacet BSDF, this seems to be exactly the same situation.
by ypoissant
Tue Mar 25, 2014 4:44 pm
Forum: General Development
Topic: Microfacet (RoughGlass) and Multiple Importance Sampling
Replies: 13
Views: 9640

Re: Microfacet (RoughGlass) and Multiple Importance Sampling

Since you are using Pixar Renderman Framework, Are you aware of the following resources: http://blog.selfshadow.com/publications/s2013-shading-course/ In particular the course notes "Physically Based Shading at Pixar" And in Pixar RPS documentation: http://renderman.pixar.com/resources/current/rps/p...