Search found 46 matches

by apaffy
Fri Jul 20, 2012 8:27 am
Forum: General Development
Topic: Veach thesis - formula question
Replies: 86
Views: 48737

Re: Veach thesis - formula question

Hi spectral, Firstly, in the "UnitConversion.png" diagram, p(w_o) is actually pdf wrt solid angle. This is why the equation has a missing cosine in this diagram. You can convert this to projected solid angle (let's call this p_\perp) as follows (paste into LaTeX to see this in a nice form - as an as...
by apaffy
Thu Jul 19, 2012 8:59 am
Forum: General Development
Topic: Veach thesis - formula question
Replies: 86
Views: 48737

Re: Veach thesis - formula question

* Understanding how the geometry term is used to convert pdfs between projected solid angle and area I've not this understanding and would be interested in explanations if possible Thanks I think the best I can do is direct you towards sections 8.1 and 8.2 of the Veach thesis, which covers this top...
by apaffy
Wed Jul 18, 2012 6:36 pm
Forum: General Development
Topic: Veach thesis - formula question
Replies: 86
Views: 48737

Re: Veach thesis - formula question

+1 to ingenious' post. I agree you just have to work through the maths yourself until it all slots into place. For me the Eureka moments were: * Understanding how the geometry term is used to convert pdfs between projected solid angle and area * Understanding how all but one of the geometry terms ca...
by apaffy
Wed Jul 18, 2012 4:48 pm
Forum: General Development
Topic: Veach thesis - formula question
Replies: 86
Views: 48737

Re: Veach thesis - formula question

Thanks, It is not what I do when I use the following formula ? L = Le * |Nl.-Wi1| |N1.Wi1| / r*r Where : x0 : point on light x1 : first hit r : distance(x0,x1) Nl : normal at x0 N1: normal at x1 Wi1= normalize(x0-x1) First, I choose a random point on the light and a random (hemisphere) direction, t...
by apaffy
Wed Jul 18, 2012 12:38 pm
Forum: General Development
Topic: Veach thesis - formula question
Replies: 86
Views: 48737

Re: Veach thesis - formula question

the same light intensity is emitted (in all direction) from the top of the cube. I'd be careful with your definitions, Lambertian reflectance produces uniform radiance, which means the same energy for each differential projected solid angle. Are you perhaps missing some conversion from solid angle ...
by apaffy
Tue Jul 17, 2012 2:22 pm
Forum: General Development
Topic: Veach thesis - formula question
Replies: 86
Views: 48737

Re: Veach thesis - formula question

Sure, I know I don't use the x(0) sample on the camera... why ? Because it run on the GPU and I would like a 'light path' for each pixel and not for a random pixel (connection between random light path and camera give a random pixel) ! It is why I first generate a ray per pixel and connect this ver...
by apaffy
Tue Jul 17, 2012 1:05 pm
Forum: General Development
Topic: Veach thesis - formula question
Replies: 86
Views: 48737

Re: Veach thesis - formula question

Your light tracing algorithm looks a bit odd, I'd expect the dual of your path tracing algorithm. Making some minor changes to connect the eye and light vertices before the light subpath is extended (to make light sources directly visible), I'd expect something like this: Light tracer: 1) sample one...
by apaffy
Sun May 13, 2012 6:19 pm
Forum: Links & Papers
Topic: Vertex Merging
Replies: 21
Views: 16628

Re: Vertex Merging

I assume the reduced efficiency over time is due to the merge radius reducing over time (as per [S]PPM), hence the MIS weight of the "merge" technique reduces and we get back to standard BDPT.

It seems like a really nice result, definitely going to have a go at implementing it.
by apaffy
Mon May 07, 2012 9:18 am
Forum: General Development
Topic: BDPT Debugging
Replies: 15
Views: 9805

Re: BDPT Debugging

Hi, some suggestions for debugging or checking consistency: * Store out separate images for each (s,t) path combination, make sure they look as expected and you haven't missed/doubled a technique. :) * Check a light path tracer converges to the same image as your (eye) path tracer. For this you'll n...
by apaffy
Wed Apr 18, 2012 4:53 pm
Forum: General Development
Topic: Fireflies in pathtracer
Replies: 6
Views: 7147

Re: Fireflies in pathtracer

Yep the fireflies will be from BSDF sampling to extend the path hitting one of these areas that are very brightly directly lit. The only way to reduce the fireflies is to find paths through these bright areas with higher probability, which is exactly what light subpaths (in a bidirectional path trac...