Odd lighting with VrayMtlWrapper as a shadow catcher

[bigmachinestudios]

I am seeing peculiar lighting/shadows using the VrayMtlWrapper as a shadow catcher. While the shadow catcher surface is catching shadows, they don't look right. The lighting of the foreground element is also off. I first noticed when rendering one of our characters against a ground plane. Not only do the darkened shadows look overly harsh, but there are also areas where the shadows seem to be illuminating the ground. I created a simplified test case and rendered 2 versions. The first is a cylidrical shape over a plane with VrMtlWrapper applied, and then composited in Fusion over a separate render of the plane with its basic material. The second is the plane and cylinder rendered together with no compositing or shadow catcher materials. The latter looks perfect but the comp using the shadow catcher has odd and harsh shadows with more severe lighting on the cylinder. Here is a sample pic:



And these are the settings for the VrayMtlWrapper:



I am running Build 4.30.02 (V-Ray Next, update 2.2 official) in Maya 2020. I am illuminating with 3 area lights and a VrayLightDome. Is there something I am doing wrong or is there a known bug in Vray Next with VrayMtlWrapper? I've also attached the scene I used to test.

[bigmachinestudios]

I believe I found the source of the problem. The denoiser render element pretty aggressively blurs the shadow from the VrayMtlWrapper. If there are settings in the denoiser to maintain its effectiveness without compromising the shadow, I would love to hear it. But in the meantime, I will render without the denoiser and then use the separate denoiser tool on the final composite, which seems to work fairly well.



I should add that while disabling the denoiser does improve the integrity of the shadows, it DOES NOT fix the lighting. There is clearly a huge difference between rendering the ground plane with the foreground versus compositing a foreground with a shadow catcher. If anyone has any info on this, I would love to hear it.

[nikolay.kusht]

I will take a look at your scene and reply back when I have more details.

[nikolay.kusht]

Sorry for the late reply, I have logged this as a bug to our system.