render transparent shadow on object to reflect in one pass?

[andy.engelkemier]

I have an object sitting on a table. I want to render the object and composite that onto an image.
The object needs to reflect the table, so I modeled it and matched the camera. Yay, it's a great match, which means the stock image isn't cropped.
I need my object to cast a shadow also.

I was hoping I could use the ground material to catch the shadow, then just below that apply an emissive to the table just for reflections. that is invisible to camera.
Well that doesn't work. The ground material is visible to reflections as it is. And applying rayMask to ground material immediately breaks the ground material, so I assume it's not actually supported. That makes sense since raymask is accomplishing something similar to what the ground material is doing already, just without options that I was hoping for.
Some software lets you give the ground material a ground texture to reflect. But here, it will reflect the environment, which is always a sphere. That doesn't work well when you have multiple objects in your scene if you can't get flatten ground to match those objects perfectly.

Anyway, what i'll end up doing is one render for catching just the shadow, then another render for getting the reflection of the table. That won't actually end up being correct though, because the reflection of the table will be missing the object shadow. But it'll look close enough for this project. But I'd like to know if there's a way to actually accomplish this.
I really wish there was a way to give the ground material a material to use for being reflected.

Keyshot needs a material override: It's this material for the camera, it's this material for refractions, it's this material for reflections, it's this material for GI calculations, etc. No reason GI needs to see your fancy bump map and highly textured brushed metal, for example. That's just adding a TON of calculations for nothing. That being said, that kind of material is likely Very complicated to program and not break things like denoise and other image adjustments.

[bdesign]

Hi Andy-

Check out reply #10 under this thread:

https://forum.keyshot.com/index.php?topic=12745.msg62516#msg62516

It's a "trick", but may help.

Cheers,
Eric