VrayPlane as Shadow Catcher causes massiv GI spill

[kosso_olli]

Hey guys,
I have a scene here causing some issues. The teapot is standing in a white environment, lit by a dome light with flat white color.
First image is with a white VrayPlane. As you can see, there is a solid and believable shadow under the teapot.



Now, when the VrayPlane is turned into a shadow catcher using the toolbar button, two things happen: The shadow under the teapot is gone, and there is a massive GI spill in white color that is very difficult to clean up.


Scene file is attached.

Matte_Shadow_Bug_v01.zip

[^Lele^]

Turning off "Matte for reflection/refraction" cures the issue.

[kosso_olli]

While this solution cures the GI spill on the teapot, it does not fix the issues with the shadow when the plane is set to shadow catcher. There are GI artifacts under the teapot:

Here with matte shadow and matte for refl/refr off:



And the plane without shadow catcher mode:

[^Lele^]

You'll have to use Brute Force.
That's a known issue with the LC's leak prevention and mattes.

[vlado]

I have some ideas to fix this with the light cache; we'll see if they work in practice.

Best regards,
Vlado

[kosso_olli]

You'll have to use Brute Force.
That's a known issue with the LC's leak prevention and mattes.

Well, it is unkown to me and most other users out there.

[^Lele^]

You forgot, perhaps.
Here's a thread on mattes from 2015, to which you replied only three or four posts down.
https://forums.chaos.com/forum/v-ray...764#post753764

[kosso_olli]

Oh wow, that was a long time ago. Anyway, will try with Brute Force.

[^Lele^]

Eheh, time flies!
Let's hope Vlado's ideas bear fruit!

[fixeighted]

Well....um....fruit from 2015 should certainly have ripened by know y'think?

[^Lele^]

Wish it was a case of sitting and waiting...

[fixeighted]

Good post in any case and I didn't realise that bf fixed it.
There was a post recently where the OP and a few others were having problems with the catcher.
Although it worked for me, those artifacts were indeed present...so this post and the linked old one adds to my knowledge pool,
which I constantly try to keep afloat in,....these posts serving as little ducky armbands

[^Lele^]

I know my forum searches aren't wasted then!