From: Germán Molina Larrain <[email protected]>
Date: June 21, 2013 8:42:14 AM PDT
Thanks for the answers Lars!
I am thinking on "one-zone" simple scenes, without furniture. I was checking out Lightsolve algorithms, and for them, this approach seem to be working well. I am thinking on something similar, but not the same.
Also, a friend of mine did some work on lighting simulations, and claimed that Radiosity was actually much faster than Radiance for those calculations.
Anyway, lets see what others can say about this... I was aware of the hybrid-stochastic-deterministic capabilities of Radiance, but I am not sure what that exactly means, so I cannot say if this would be faster or not.
THANKS!
German
2013/6/21 Lars O. Grobe <[email protected]>
Hi German!
> I am thinking on implementing a hybrid methodology between Radiosity
> method and Ray-tracing, for accelerating some calculations (by giving up
> accuracy, maybe)
Did you think about in what use cases radiosity may be faster, and in
which it wouldn't? And are you aware of the "hybrid" rendering approach
used by Radiance? Especially the way that the ambient cache is working
as a means to accelerate the stochastic diffuse-indirect calculation
that a radiosity renderer aims at?
> I think I can make algorythms to subdivide polygons into meshes,
> however, what I do not know how to do is:
I think most of this is already happening when you are using the ambient
cache.
> *1.- Calculation of View (Form) Factors:* I guess a straitforward way is
> to calculate them by randomly sending rays from one surface to the rest
> of them, but I do not know how to do that (or use octrees). (k/N would
> be the view factor Fij... where k is the number of rays that falled into
> j from i, and N the total number of rays sent)
If you want to do this using scripts and the available tools, you could
step through all surfaces in a scene file. There are tools to do the
sampling available.
> *2.- Render:* After I have the Radiosities of every polygon. How can I
> make a render? I guess I can use *vwrays *somehow, but I am not sure how
> to check which polygon am I "seeing", in order to use the calculated values.
You can tell rtrace to output object names instead of radiance or
irradiance values. You can also get both the name of the object and its
radiance. This would even allow to add the radiance value of a scene
with -ab 0 and the precalculated "radiosity" value. Somehow what most
radiosity renderers do to achieve sharp shadows (they add a
raytracing-step for direct calculation).
Still I have doubts that this can be faster than the current
implementation.... 
Cheers, Lars.
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