Add Shadow Catcher – x10+ render time jump

[KernitTheFont]

Hi all,
Does anybody have an idea why a render would jump from 10 minutes to nearly two hours, just from making the background sweep a shadow catcher? Some kind of bug maybe?
I'm using a shadow pass for the time being as a workaround. Hope someone can help me understand why, because it's baffled me.
Thanks,

[YunalZobu]

Could you share a simple scene file, in which you have those render times?

[KernitTheFont]

Sure, I'll DM it across. Thanks Yunal.

[aleksandar.kasabov]

Hello KernitTheFont,

Would you mind sharing the scene with me as well so I can have a look? Do you experience the issue with a specific scene only or any scene? Also, please let me know what are the exact versions of V-Ray, Cinema4D, and OS that you have installed. Thank you.

[KernitTheFont]

Shared – thanks Aleksander

[KernitTheFont]

Do you experience the issue with a specific scene only or any scene?

Just tested another scene and I'm seeing the same time bump. ¯\_(ツ)_/¯

[KernitTheFont]

Hi YunalZobu / aleksandar.kasabov , Any joy working out what's going wrong?

[fixeighted]

This has been an issue with 3ds Max also and seems to be that it takes a long long time to clean up the alpha.
So much so that I've tried to find workarounds for certain 'studio' shots.
If that is what you're doing then a possible solution to getting a GI-like contact shadow is to use a distance tex/dirt.
Maybe not ideal but certainly works well enough in my situations and doesn't take silly times to finish

[KernitTheFont]

Thanks Fix. Yeah for one of my renders I saved out an object alpha and added it to one of the shadow render elements (can't remember which one). Seemed to be a half decent workaround. Still, would be nice if there was a fix in the pipeline, especially when working on animations. Just more faff you have to remember.

[aleksandar.kasabov]

Hello KernitTheFont,

I have checked your scene and it seems that the long render times are caused by the glossiness amount in the material, applied to the shadow catcher object. If the glossiness is set to 1 or there isn't a reflection at all, then the render times are the same as when the Matte surface is disabled.

I have reported this to our developers (bug ID: VC4D-1258 ) and I will let you know once we have more information. Thank you!

[KernitTheFont]

Thanks for looking Aleksander. I'll keep that in mind for future renders