Edge between the object and shadows

[ensar_huskovic]

Hi,
I am try to integrate an object + shadow rendering into a backplate. After I set everything up in the VFB, I want to render just the object and shadows (hopefully in a single rendering) and then comp it in Affinity with the backplate, so that vfb does not affect the backplate.
When I render object+shadows on black environment and then comp it I get the problem of white edge between the object and the shadow - see attached.

What is the best worfklow at this moment since alpha options are not fully supported on GPU? I need a perfectly clean result and backplate untouched.
Thanks

[ensar_huskovic]

Anyone knows how to fix this?

[Morbid Angel]

I'm not familiar with gpu enough, but generally you need to render object invisible to camera (so just shadow) then object it self (two pass render) then it will comp. But the white edge you see there is not just around the shadow. I think you are rendering the object against non black bg, is that true? in that case you might encounter premultiplication issues.

[ensar_huskovic]

Thanks for your response. I know the 2 pass workflow but as i have hundreds of these to render i wanted to see if i can get away with a single rendering for both the shadow and the object. At least i think that is one of main advantages of shadow matte.
I rendered against black and white bg but none of it works correctly.

[Morbid Angel]

can you send me a scene with a simple example?