OTOY Forums

Hi,
I made a simple scene to illustrate my question:
I made a sphere, put a glass material on it. Beneath it is a plane, which acts as a shadow catcher. Now I would like to reflect the real color of the shadow catcher (which in this case is a simple green) in the sphere. But all I can see are some strange reflections from the HDRI that lights the scene. Anyone knows what to do?

Best, Oblivion

Hard to tell exactly what you are after, but the render layer setup should give you better results
https://docs.otoy.com/Cinema4DH/C4DPlug ... Passes.htm

ok to illustrate this even a little bit better, I made the same scene in blender. on the left side you can see the rendered view with the sphere. the plane under the sphere acts as a shadow catcher, but the green diffuse channel of the plane is also shown mirrored in the sphere.

That seems similar to the first one, but what's not clear is what you want for the final output.
You'll get green reflection if you turn off shadow catcher. The shadow will still be there, it will just be on the green.
If you're trying to output for composting then render layer would be better than shadow catcher.
Put your sphere on object layer 2, and then render that layer with black shadows ticked.

I can see why reflections in the shadow catcher would be a desirable function.

Although the correct method for final output would be to render everything as layers and assemble in comp. It would also be nice to be able to use the shadow catcher as a temporary way to preview how the scene integrates with a backplate while lighting in the live viewer.

A good example of this is integrating a CG car over a photo backplate. It's great to see the shadows using the shadow catcher but it's normal to camera project the backplate onto the ground plane so that some of the ground reflections are visible on the car. Unfortunately when shadow catcher is enabled any texture on the ground plane is ignored. It's like the shadow catcher option assumes you are using the environment/hdri as your background and require only reflections the environment dome.

The way I work around this is to disable shadow catcher and project the backplate onto my floor plane. This does create an obvious brightness difference between the backplate and the floor projection but it does allow for accurate shadow and reflections between the floor plane and the car while still being able to see the backplate for lighting setup purposes. Then use layers to created the passes I need to assemble in comp.

Hopefully that all makes sense but basically what i'm saying is that I think this is a valid request even if just for helping setup lighting in the live viewer before eventually using established render layers workflows for offline rendering.

that explanation makes total sense. in my case, I need to track a giant pin to drone shot of a mountain. I made a mesh reconstruction of the mountain in C4D, and I want it to catch the shadow of the pin as well as act as reflection for the pin (which has a metal material on it).

so, yeah, feature request