[Radiance-general] Radiosity method implementation on Radiance

[Germán Molina Larrain]

Thanks for the answers Lars!

I am thinking on "one-zone" simple scenes, without furniture. I was
checking out Lightsolve
<http://www.phil-seaton.com/#/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 <grobe at gmx.net>

> 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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