Search found 46 matches

by apaffy
Wed Aug 08, 2012 4:45 pm
Forum: General Development
Topic: MIS on the GPU
Replies: 41
Views: 27266

Re: MIS on the GPU

BTW, With the recursive MIS computation, is it a problem if I start the camera path at the first scene hit. By example, I don't want to connect the eye directly to the light (see image, I don't do the connection in red, my camera first throw a ray in the scene and find the first hit). Should I modi...
by apaffy
Mon Jul 23, 2012 8:08 pm
Forum: General Development
Topic: Veach thesis - formula question
Replies: 86
Views: 48737

Re: Veach thesis - formula question

But how MIS can fix the problem ? The problem is due to very small value of ||x-x'|| and G is not part of the path pdf ! G is not related with the way we sample... there is no relation ! What do I miss ? Due to MIS, that sampling technique will be assigned a small enough weight that the Monte Carlo...
by apaffy
Mon Jul 23, 2012 12:26 pm
Forum: General Development
Topic: Veach thesis - formula question
Replies: 86
Views: 48737

Re: Veach thesis - formula question

If you read the Kollig and Keller paper, you'll see how this recursive bias compensation technique can be reformulated as a weighting scheme for multiple importance sampling in a bidirectional path tracer.

Maybe not directly helpful for you, but I found this to be really insightful.
by apaffy
Fri Jul 20, 2012 4:35 pm
Forum: General Development
Topic: Veach thesis - formula question
Replies: 86
Views: 48737

Re: Veach thesis - formula question

I have always considered the film/pinhole to be geometrically planar, in which case yes I have included a cosine term to compute the pdf wrt projected solid angle (as the equations require). I've always viewed this as additional vignetting due to points on the film away from the center not being per...
by apaffy
Fri Jul 20, 2012 3:37 pm
Forum: General Development
Topic: Veach thesis - formula question
Replies: 86
Views: 48737

Re: Veach thesis - formula question

Personally I would keep the equation generic by keeping Le(x0 -> x1)/p(x0) and We(x5->x4)/p(x5) in there, which you can then specialize in code for the light/camera you are going to use, but this looks correct given your light/camera assumptions.
by apaffy
Fri Jul 20, 2012 3:02 pm
Forum: General Development
Topic: Veach thesis - formula question
Replies: 86
Views: 48737

Re: Veach thesis - formula question

Ah great :-P, In a previous post from Ingenious, he tell that in BDPT the connection segment is deterministic and so P_\perp(x1 -> x2) = 1 and P_\perp(x4 -> x3) = 1 ! The deterministic connection is between x2 and x3! x1->x2 and x4->x3 are sampled (at x1 and x4 respectively)! 1/pi is the pdf in sol...
by apaffy
Fri Jul 20, 2012 2:52 pm
Forum: General Development
Topic: Veach thesis - formula question
Replies: 86
Views: 48737

Re: Veach thesis - formula question

Okay, professor.... finally I have : I'm just trying to point you towards the method for the answer, sorry if the to-and-fro is annoying. :) And I agree with your result in "bdpt_solve3.png"! If I understand, we also have (compared to your previous post) : P_A(x0) = 1 P_A(x5) = 1 P_\perp(x1 -> x2) ...
by apaffy
Fri Jul 20, 2012 2:11 pm
Forum: General Development
Topic: Veach thesis - formula question
Replies: 86
Views: 48737

Re: Veach thesis - formula question

You'll end up with an equation that contains: * P_A(x0) and P_A(x5) First line is great! Something happened to your maths between the first and second lines, your pdf conversions are not correct. Your final equation will contain P_A(x0) and P_A(x5) as I noted above! Edit: actually I already wrote d...
by apaffy
Fri Jul 20, 2012 11:58 am
Forum: General Development
Topic: Veach thesis - formula question
Replies: 86
Views: 48737

Re: Veach thesis - formula question

Also please when you write "pdf" state the measure. For example: Path space pdf = pdf wrt area product measure P_A(x) = pdf wrt area at x P(x -> x') = pdf wrt solid angle of ray x->x' at x P_\perp(x -> x') = pdf wrt projected solid angle of ray x->x' at x This really helps to not lose track of what'...
by apaffy
Fri Jul 20, 2012 11:49 am
Forum: General Development
Topic: Veach thesis - formula question
Replies: 86
Views: 48737

Re: Veach thesis - formula question

Hi spectral, glad to hear things are starting to get more clear. Your diagram is a great start, but I don't agree with your equation for the final Monte Carlo sample. As ingenious posted above, what you need to write down is: * The path contribution. This has great symmetry being Le G f G f G f G f ...