Chris Cason <del### [at] deletethistoopovrayorg> wrote:
> Invisible wrote:
> > Actually, that's an interesting point... Would presumably mean the very
> > first frame still takes 20 minutes, and all the subsequent ones are
> > reasonably fast unless/until you expose new geometry.
>
> well, it might be interesting to work this out at some point ... if you were
> comparing a scene lit completely with radiosity (and presuming that the
> radiosity cache had already been built) against one with several traditional
> point light sources, at what point does the savings of not having to trace a
> shadow ray overcome the cache lookup time?
>
> I would suspect that the answer is 'very early', except perhaps in very
> simple scenes with little geometry. The more geometry is there, the more time
> spent doing lookups of the bounding structure (BVH or BSP) against each
> shadow ray - the more light sources, the more time, with the relationship
> being fairly linear.
>
> the rad cache lookup, however, would not suffer from this problem.
>
> therefore it is entirely possible that, as counterintuitive as it may seem,
> there is potential for a scene with global illumination to be *faster* in
> interactive rendering than one without.
>
> -- Chris


I used the POV-Ray 3.6 Radiosity Demoscene with the "fast"- Radiositysetting
to test it...
To get a "real" Framerate for Radiosity I tried measure the time to render
the Frames 400 to 900. The Result was about 4,23 FPS at 160x120 Pixels.
I started after a few complete loops at Frame 400 to be sure, that all
necessary Radiositysamples are calculated.
Withour Radiosity, only with the "Light 2", I get about 11,5 FPS at 160x120
Pixels.

I know that the Radiosity is very alpha (it works in this scene) - how much
faster it may get until the next full release?

-- Thomas

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