[Bf-committers] Ray-tracing soft shadows, a speed-up

[Nathan Vegdahl]

   I haven't actually looked at the source code, but it think that the
soft-shadows feature in the ray tracer is doing redundant sampling when OSA is
turned on.

   Example: if you set the shadow samples to 4 (i.e. 16 actual samples) and you
set the OSA to 16, then the ray tracer is tracing 16x16 (256) samples per
pixel.  This is because it is tracing 16 rays (for the soft shadows) per each
single anti-aliasing sample.

   To optimize this, you can use the same rays for both the anti-aliasing and
the soft-shadows.  In the case that the OSA samples and the shadow samples are
not set to the same number, simply use the larger of the two.

   Oh, and thank you very much, Ton, for implimenting the raytracing!  Even as
it is right now, it is useful!

--Nathan Vegdahl

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