Environment Lighting canvas renders black ground

thoreandan

I like to use Iray light group canvasses to composite my images, but when I use an HDRI I run into this problem: the environment lighting canvas renders an entire section of the background in flat black. I've had this problem for years and assumed it was a VRAM issue, but just now I rendered a scene with a tilted camera and it's finally obvious to me that these black sections show up where the ground plane would be. I would just turn off the ground (not sure if that would work), but I need the ground turned on to catch shadows.

Does anybody have any ideas how to fix this without having to render the same scene multiple times? I've sometimes used photoshop to add the background hdr file in afterwards if I just needed the HDRI for a background. But in this case I really need the contribution of the HDR environment lighting on the character. I could try to strip out the background from the env lighting canvas and use the effect on the character only, but this would lose the shadow cast by the env lighting itself, and getting a reliable alpha canvas out of Iray to do this is difficult or impossible depending on things like hair translucency.

The attached screenshot of the environment lighting canvas after loading it into PS shows what I'm talking about.