Shadow Catcher Material + Motion blur

[killer000sp]

Hi, I need help regarding Shadow Catcher Material, motion blur, and compositing in After Effects. I have created a simple grey room with a moving box in it. There's one rectangular light above and the CoronaCam with motion blur enabled.

I rendered and saved the background without the box and then assigned the Shadow Catcher Material to it. So I have separate background ready and now I'm trying to tweak the settings of the Shadow Catcher Material of the background – the output should be just motion blurred box and shadows (PNG with an alpha channel).

I made several outputs with different settings and composed them with the background in AE but I just can't get rid of the black color in blurred part around the box. When I set Shadow Catcher to "Always transparent" the motion blur around the box is OK but it's obviously without the shadows under the box... Look at TEST.png where you can see different outputs from AE.

I tried to put my rendered background as backplate in Shadow Catcher Material, I tried to turn on and off Direct visibility override in Render Settings (with black color) but nothing works... I'm pretty certain that the solution will be trivial but I just can't figure it out. Is there anything I'm missing? I tried to search on Google and also here on forum but the only thread that is similar to my issue is this (but it's in Cinema 4D):
https://forum.corona-renderer.com/index.php?topic=30023.0

For comparison, I have also attached BEAUTY.png, which shows the entire scene rendered with the background and the box (directly saved from the VFB).

I am using 3DS Max 2024.1 with Corona 10.

[Aram Avetisyan]

Hi,

Let's simplify the task: you need to have a render with motion blur and shadows, which then needs to be composited over some background. You need to get as close to original results as possible.

Well, you kinda did in some of the test. It just appears that shadows are too dark maybe, or the GI is too much from the red box. Nevertheless, I think you are doing everything right, you just need to change some color parameters for Shadows catcher, or the Shadow amount of it, or just use RaySwitch material for tweaking separate parts of the shadowcatcher.

You can even do this by simply using a color correction for the alpha of the image - to make the shadows less opaque and hence brighter over a white background.

If you need a more detailed and technical help, it is best to send us a ticket here:
https://support.chaos.com/hc/en-us/requests/new