See image for reference.
Left side is a v-ray plane set to shadow catcher, has an alpha an was composited in AE on a BG.
Right side is a v-ray plane with a simple grey material, opaque alpha (a simple visible object), was composited in AE set to multiply on a BG.
Render time is close to the same, but the results are vastly different. If I want an equivalent result with the shadow catcher/alpha I need to reduce my noise threshold to a ridiculously low number and suffer extreme rendertimes - which is not needed for the rest of the scene, only the shadows.
It is frustrating as I don’t really need to separate all the shadows out for most projects, except for this shadow/noise issue.
Can’t share this project but problem should be easy to replicate.
Found this old thread that details the same issue, but ends with no answer:
I’m also facing this problem. The only work around i have found right now (other than lowering the noise treeshold) is to raise the “Subdivision Multiplier” of the matte object to something like 3-5. This parameter is in the VRay Property when you right click on a object.
It not ideal as there are still some noise but less than before.
@legi008 I totally missed the boat (or forgot) about the option for local subdivs in VRay Properties. This is super helpful - thanks!
I did a new scene to test just the shadow catcher though - and here the noise problem was not nearly as big an issue as in my client scene. I suspected an HDRI was the culprit but turning it off made no difference. Would love to find out what is causing the noisy shadow catcher - which seems to be only in certain cases.
@HenrikBC Could you send the scene via the contact form so we can take a look? Mention me in the subject and include a link to this thread in the message.
@hermit.crab I have reduced the scene and sent it according to your specs. Thanks!
Thank you for the provided scene. There does seem to be more noise with a VRaySun and a black background environment color. I’ve logged the issue (internal bug-tracker id: VMAX-11057) for our developers to investigate. Changing the Background color to another color may be used to reduce the noise.
