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bidirectional path tracing
show user profile  zeefusion
I have been reading up on bidirectional path tracing and to no surprise its hurting my head a little. As I understand it it combines tracing rays from camera and tracing rays from lights.

Is this then in essence unbiased? How does this differ from say brute force? Is iray, VrayRT, Embree built on bidirectional or is there yet another way of rendering that they use?

I cant seem to find a clear summary of how each rendering tech works.
read 469 times
1/18/2012 3:01:30 PM (last edit: 1/18/2012 3:01:30 PM)
show user profile  Garp
Tracing from the camera ensures that only color values for the visible surfaces will be computed.
Of course, secondary rays might - and probably will - touch surfaces that are not directly visible from the camera. This ensures proper color bleeding, for example.
A clever use of ray tracing from the light sources as well can allow to discard surfaces not directly lit and thus avoid computation of useless secondary rays.
I haven't read much on it though. Don't take my word for it.
AS should know a lot more.




read 445 times
1/19/2012 2:55:25 AM (last edit: 1/19/2012 2:55:25 AM)
show user profile  Mr_Stabby
its just an optimization to generate some natural phenomena more efficiently. stuff like diffuse radiosity and caustics generate a more accurate effect when traced from the light while reflections and refractions are much, much faster when traced from the camera. If you take MR for an example its probably most appropriate to call it a tri-directional tracer since it traces from camera for all reflections/refractions and direct shading, traces from light GI and caustics, traces from geometry AO and the combination of all of these while doing FG. All the gpu brute force renderers are to an extent bi directional since they spend around 99% of their time tracing from light to camera and the remaining time tracing from camera to geometry but it wouldnt be fair to call them bidirectional in the same sense as cpu renderers are since cpu renderers deliberately use the various techniques to most efficiently render the scene

read 440 times
1/19/2012 3:39:46 AM (last edit: 1/19/2012 3:39:46 AM)
show user profile  zeefusion
What do you mean "brute force GPU"? I am getting a little muddled here...what about CPU brute force?

mental ray is CPU and GPU, VrayRT is CPU or GPU. Are you saying some are bi directional where as others are tri directional?
read 430 times
1/19/2012 8:43:14 AM (last edit: 1/19/2012 8:43:14 AM)
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