[Bf-cycles] Lightprobe importance sampling

Brecht Van Lommel brechtvanlommel at pandora.be
Wed Dec 28 13:46:57 CET 2011

Yes, this sounds right, the environment should be added as another
light type. It can be added to the light_distribution texture,
initially with just a fixed overall importance, and then in a next
step split up into smaller pieces with different importance based on
pixel intensity.

For the background shader evaluation in kernel_path_integrate, MIS can
be added in a similar way as is done in indirect_emission.


On Wed, Dec 28, 2011 at 8:11 AM, Mike Farnsworth
<mike.farnsworth at gmail.com> wrote:
> Just a quick heads-up, I'm starting to tinker with cycles, in particular I'm
> trying to add support for Pharr/Humphries style importance sampling of
> environment images.  I wanted to make sure I had a clear understanding of
> what I need to change to make it happen.
> It appears to me that the path integrator just samples the environment on
> ray misses based on importance sampling the BSDF.  The only time MIS and
> light importance sampling come into play are when doing direct lighting.
> The environment doesn't count as a 'light' in cycles, thus it never even has
> a chance to offer important directions and a PDF.  So, to start, I need to
> make the environment also appear as a light (useful for images and the sky
> background, for example).  Once that is done, I can precompute some
> importance information, stuff it in a texture, and go from there?
> Let me know if I'm totally barking up the wrong tree.
> -Farny
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