Shadow catcher "For Compositing" mode introducing noise.

[jjduncs]

I'm wanting to use the 'for compositing' mode with the shadow catcher mtl. Ive got the override visibility set to black (backplate bitmap unchecked).

The issue I am getting is that using this mode, it is producing more noise than when the alpha mode is on 'always solid' and the backplate is in the direct visibility override.

The left image has shadow catcher with 'for compositing' alpha mode and you can see the extra noise/fireflies that are appearing. The right image is when alpha mode is 'always solid' and the backplate is in the visibility override.

Both renders are after about 7 passes.

A bit of the backplate is showing on the left image and Im assuming this is just from reflected GI from the 3d objects. With the alpha mask this is all erased so I don't think that is part of the issue.

Not sure if this constitutes a bug but it is definitely the alpha mode in the shadow catcher that is causing this difference.

[maru]

[this is not an answer, just a note]
more details are in this thread: https://forum.corona-renderer.com/index.php/topic,5242.msg37776.html#msg37776
Looks like it was caused by pt+hd. I was unable to recreate it. UHD cache possibly fixed this. (?)

[Ondra]

That is fairly unconverged image, and there are similar fireflies in the second image, just more scattered. Does the noise eventually goes away?

I could take a look at the scene if you wanted

[jjduncs]

It's an old scene now but it was the HD Cache that was causing it. Noise didn't go away after cooking for ages, but on PT + PT mode it was fine.

Cheers

[Ondra]

it should still work with caching - if there is still problem when using UHD cache (the new cache in Corona 1.0), could you send me the scene so I can investigate?

[jjduncs]

Yep no worries I'll have a crack at it tomorrow.

[Ludvik Koutny]

Any updates on this? Or can i close the report?

[Ludvik Koutny]

Inactive topic, moving to resolved. If you still experience the issue, feel free to create new bug report.