shadow catcher appearing in vector pass #111149

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opened 2023-08-15 21:15:31 +02:00 by michael campbell · 4 comments

michael campbell commented

2023-08-15 21:15:31 +02:00

System Information
Operating system: Windows-10-10.0.19044-SP0 64 Bits
Graphics card: NVIDIA GeForce GTX 1070/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 536.99

Blender Version
Broken: version: 4.0.0 Alpha, branch: main, commit date: 2023-06-30 00:04, hash: e73a9a6a7d7b
Worked: (newest version of Blender that worked as expected)

Short description of error
vector data is present for the shadow catcher objects. This needs to be omitted otherwise the vector blur node can't be used to add motion blur to the 3d elements, because unwanted motion blur will be added to the environment pass. If it a backplate was used then it wouldn't be a problem, transparent film could be set, and the blur would only affect the geometry. This also has an issue though, because the vector blur pass modifies the alpha too, so the shadow catcher vector could still affect the blur of the 3d geometry even if it's hidden by transparency.

Exact steps for others to reproduce the error

open attached file
go to frame 10
open the compositor
render still frame
check the compositor backdrop (shows vector data for the shadow catcher).

Same result if film is set to transparent.

**System Information** Operating system: Windows-10-10.0.19044-SP0 64 Bits Graphics card: NVIDIA GeForce GTX 1070/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 536.99 **Blender Version** Broken: version: 4.0.0 Alpha, branch: main, commit date: 2023-06-30 00:04, hash: `e73a9a6a7d7b` Worked: (newest version of Blender that worked as expected) **Short description of error** vector data is present for the shadow catcher objects. This needs to be omitted otherwise the vector blur node can't be used to add motion blur to the 3d elements, because unwanted motion blur will be added to the environment pass. If it a backplate was used then it wouldn't be a problem, transparent film could be set, and the blur would only affect the geometry. This also has an issue though, because the vector blur pass modifies the alpha too, so the shadow catcher vector could still affect the blur of the 3d geometry even if it's hidden by transparency. **Exact steps for others to reproduce the error** 1. open attached file 2. go to frame 10 3. open the compositor 4. render still frame 5. check the compositor backdrop (shows vector data for the shadow catcher). Same result if film is set to transparent.

shadow catcher vector bug.blend

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michael campbell added the

labels 2023-08-15 21:15:31 +02:00

YimingWu commented

2023-08-16 04:09:41 +02:00

Member

Can confirm. Not sure if it's a limitation of the shadow catcher tho

Can confirm. Not sure if it's a limitation of the shadow catcher tho

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Lukas Stockner commented

2023-10-05 01:37:13 +02:00

Member

This isn't specific to the Vector pass, currently shadow catchers write all data passes as if they were regular geometry - only Combined is affected.

To be honest, I'm not sure what kind of compositing setup this would be a problem in, and why you can't just mask it out if needed using either the Alpha channel or e.g. the Object Index or Cryptomatte pass?

This isn't specific to the Vector pass, currently shadow catchers write all data passes as if they were regular geometry - only Combined is affected. To be honest, I'm not sure what kind of compositing setup this would be a problem in, and why you can't just mask it out if needed using either the Alpha channel or e.g. the Object Index or Cryptomatte pass?

michael campbell commented

2023-10-05 03:19:51 +02:00

Author

I can get quite close that way, but I struggle to get avoid artefacts where the shadow catcher edge is and around the object:

Using cryptomatte is a bit worse because it's anti-aliased:

I can get quite close that way, but I struggle to get avoid artefacts where the shadow catcher edge is and around the object: ![image](/attachments/64a498e9-c3c7-4ff3-a3b4-76cbd38133cf) ![image](/attachments/ae977477-6418-4612-9db4-38e4db89e757) Using cryptomatte is a bit worse because it's anti-aliased: ![image](/attachments/8ec74fbe-66f4-4b49-86a9-3fe6db7e9a1e)

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michael campbell commented

2023-10-05 03:29:20 +02:00

Author

although I think close this down as invalid, because often you do want to add motion blur to the shadow. Although when using the shadow catcher pass, it does seem to suffer the same artefact at the transistion between the shadow catcher and the environment (horizontal line in the middle of the cube)

although I think close this down as invalid, because often you do want to add motion blur to the shadow. Although when using the shadow catcher pass, it does seem to suffer the same artefact at the transistion between the shadow catcher and the environment (horizontal line in the middle of the cube) ![image](/attachments/9c22fc7d-48ab-42b6-8bbd-3e36c8d7b1b1)

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Iliya Katushenock removed the

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Reference: blender/blender#111149

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