Shadow Catcher Issue on Background - please help

[alan_jurek]

I am trying to render tiles on a piece of canvas background and have the shadows appear to affect the background but I am getting this white around the tiles and not just the shadows as intended. Anyone understand what I am missing in my settings? I am using a Dome light and have it set to invisible. But the same issue occurs with CPU or GPU and global illumination.

Thank you

[iva_mancheva]

Hello, alan_jurek ,

I would like to ask you to try setting "Receive GI" of the Wrapper Material to 0 and see if the bright spots are still there. Also does the issue occur only with Interactive Rendering or with Production Rendering as well?
Thank you!

Kind regards,
Iva

[natalia.gruzdova]

Hello Alan,

Do you set your background image via V-Ray Frame Buffer Layer Background or somehow otherwise?

Can you please check your normals direction: in Rhino you can click Analyze direction to see if they are facing up. If not, use Flip command to revert them for the object that is used as a Shadow Catcher.

Please see this example and let us know if that helped.

[alan_jurek]

Hi Thank you for attention to my problem. I have tried reducing the GI to zero and got the image shown. This was a production render not interactive so it happens in all render modes. I also have checked my normal direction. I added the background in the v-ray frame buffer linked to a file on my computer.

[natalia.gruzdova]

You have to create a plane underneath those tiles and apply Wrapper material to this plane so it will become a Shadow Catcher.

On my previous screenshot you can see that blue planes are casting shadows and red plane is catching their shadows (with Wrapper material and its normals are facing up).

[alan_jurek]

I did have a surface sorry it was just too big so i shrunk it to show the normal direction and I am still getting a undesired result. photos to show results. you can see the edge of the surface where it should be transparent and not white as it is showing. Sorry but I am perplexed as I have followed all the directions and I am not getting anywhere. Do you have a work around in the mean time?

[natalia.gruzdova]

In this case it would be better if we can take a look at your scene and its setup.

I have opened a ticket for you #52729 with the email you used here on forum.
Please check your email and follow instructions from the letter.

[Micha]

alan_jurek I have some problem to use the shadow catcher too from time to time. For me it helps to load the material fresh from the material library, apply them and don't touch any parameter. It should work like expected if lights and dome lights are used. I have experience with the GPU mode only.

[natalia.gruzdova]

Thank you Micha for your comment, it was very helpful and thanks alan_jurek for providing the scene.

Upon testing it we were able to solve the issue by generating new LightGen, which led to finding the cause of the issue - high Exposure values. In the original file Film Sensitivity (ISO) was set to 1649 and decreasing the value to 50 solved the problem: here is an example.

This was logged into our system as VRW-3819 and linked to VMAX-12511.