I have a pass with plants, an HDRI dome light and a ground plane. I do not want the ground-plane to be rendered, but it should hold out plants under ground and should block light from the bottom of the HDRI. I haven’t yet found a way (visible to camera = off/on, alpha=1/0/-1, etc.) to keep the ground-plane from appearing in the z-depth element. Is there a way to keep the ground-plane out of the z-depth element, or do I need to create a second pass with the ground-plane hidden just for a z-depth of the roots?
Use the matte object tick box in vray properties, use alpha -1 and also tick off the “gen render elements” option!
A ha! Thank you thank you, after years of working around it, a single checkbox was all I needed.