Add Shadow Catcher material support

[george-lim]

Hey there!

It would be super awesome if you could add a shadow catcher material or property to the material so that we can have built-in support for materials that catch shadows but are unaffected by light. I don't think that's possible to do right now without making a custom shader, and I've been struggling with that using the core library haha (I looked at the logo example, as well as source for Physical Material but a lot of it feels very foreign to me)

My goal is to have a transparent ground plane catch shadows from a 3D model, but ignore other lighting. If you could build this feature in natively that would be awesome 🙏

Lots of other renderers have built-in support for this, like Unity and Three.js :)

[asny]

I'm not sure I understand 🤔 what will you use the catched shadows for? It sounds a bit like a shadow map, which is already supported. Or maybe it's a bit different but I guess you can use the same approach, ie render the shadow into a render target and use that result as a texture.

[george-lim]

It's to implement something like this, where I have the transparent floor that catches shadows, but doesn't itself emit light (otherwise the floor would brighten, removing the illusion of the floor being the same color as the background)

I managed to figure this one out using a custom shader, but I'm still having trouble with Mixamo animations which is a blocker for me if you have time to take a look 🙏

I think we can close this issue for now since I managed to find a way around it

[asny]

Yeah, ok, that's a very special use-case, but let's leave it open, this is probably a fun task to do 🙂