[Bf-cycles] Issues with light path node and HDR lighting

Brecht Van Lommel brechtvanlommel at pandora.be
Thu Aug 22 06:08:41 CEST 2013

Basically intended yes, I'd like it to work better but I don't know a
good solution at the moment.

The world by default will have indirect light sampling, which gives
you diffuse/glossy/transmission rays. If you enable multiple
importance sampling, it will also start using direct light sampling
with shadow rays, and the lighting will be a mix of these two light
sampling methods. So only part of the lighting will be considered
shadow rays, this is true for any lamp with multiple importance
sampling too actually.

The reason indirect light sampling rays are considered
diffuse/glossy/transmission rays is because we use the same rays for
indirect light sampling as we do for diffuse/glossy/transmission
bounces. This means we can shoot fewer rays but also means this shadow
ray check fails in some cases..

On Wed, Aug 21, 2013 at 7:14 PM, Matthew Heimlich
<matt.heimlich at gmail.com> wrote:
> Another user brought it to my attention that when using HDR lighting the "Is
> Shadow Ray" trick for getting transparent shadows from glass doesn't work.
> You have to actually turn on caustics. Is this intended?
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