Ray Bellis wrote:

> Curiously these models all seem to describe ways to approximate the 
> resulting light intensity fall-off for direct ray-tracing to light sources.


Not sure if the wikipedia article was the best to cover path tracing
needs. But at least pbrt/Luxrender has implemented Blinn stuff. And it
seems good (and definitely works for any light arriving to a point, not
just direct)

> I guess that's the advantage of the Monte Carlo method - if you're going to 
> cast millions of rays you can afford to average out the results numerically, 
> rather than use a mathematical approximation.

Yeah, and with modern multi-core CPUs Monte Carlo is actually possible.
You get good image usually in hours and more the cores we get, the
better. This stuff scales perfectly.

> Do you happen to have the geometry of your sample images available?  I'd 
> like to try to create the same scenes to compare results.

Not at present. I still try to figure out a few problems in my code.
When I know the results are truly unbiased and accurate, I can put a few
simple test scene geometries somewhere and the output.

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> Yes, that is correct. The renderer has to have a list of light sources. I also
> did first what you do now: light sources are normal objects with emission. And
> all images on my page are rendered that way. This "new" method is great because
> it improves speed so much. It is worth implementing.

I think the new feature is working properly now. Still have to test a
bit more. But the speedup is really astonishing. The newest image (the
grid of colorful blocks) on my site was first rendered in over 24 hours
with the old and slow method.

With the new direct lighting method I can achieve same noise levels in
less than hour, more like 30minutes! Than is more than one order of
magnitude speedup! And the smaller the light source is, the bigger the
difference gets.

W00t.

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