nemesis <nam### [at] nospamgmailcom> wrote:
> Radiosity is an old algorithm, from before Photon Mapping

  Photon mapping global illumination has already been tried, and it didn't
work too well. The results were much worse than the stochastic technique
currently used.

> you can't, for instance, save the
> radiosity and then try to take a shot of the scene from another angle,
> because areas occluded from the original angle will appear awkward.

  The whole idea of the stochastic algorithm used in POV-Ray is that you
*can* save the results and then render from a different angle and have
POV-Ray only calculate the necessary additional samples for that angle.
If the save/load feature is not doing that, then maybe file a bug report?

  The specific implementation in POV-Ray might be slightly lacking in some
areas, for whatever reason, but that doesn't mean the algorithm itself is
not sound.

  You make it sound like it's a bad idea to calculate GI samples only for
the visible scene. I'd say it's the exact opposite: That's exactly what
*want* to do. If you calculated GI for the entire scene, then the Sun would
probably die before it finishes if the scene is large enough. (Besides,
how would you limit the GI calculations given that POV-Ray supports infinite
surfaces?)

  A renderer called Radiance successfully implemented the exact algorithm
which is also used in POV-Ray, and Radiance has been used for architectural
lighting simulations and other such applications which require accuracy.
If you search for Radiance pictures, you'll find out that they look quite
good.

  I'd say that rather than drop the algorithm, what's needed is a complete
rewrite. Read the original paper by Greg Ward, and study how Radiance did
it correctly and what POV-Ray is doing incorrectly, and fix the problems.

-- 
                                                          - Warp

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