Multires results in a very funky "Pointiness" behaviour #90480

System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: NVIDIA GeForce RTX 3060/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 471.11

Blender Version
Broken: version: 2.93.1, branch: master, commit date: 2021-06-22 05:57, hash: 1b8d33b18c
Worked: Don't know but i've tested with 2.93, 3.00 and 3.00 Cycles-X

Short description of error
Weird rectangular patterns all over the mesh and some bright dots when using the pointiness option from the geometry node.
I subdivided a mesh with multires and used some brush alphas for skin details. Thats all what i did. Don't know why the pointiness node creates such patterns and those bright dots (which are only visible at the highest multires level but not the lower ones).

Exact steps for others to reproduce the error
Download and open the blend file I prepared here. Go to shaded view (cycles) and look at the mesh. The problem occured once in the past but it doesn't happen all the time. I didn't sculpted those patterns, they are the result of using the pointiness option in the geometry shader node - i don't know where they should come from.

Test File:
multires pattern glitch.blend

Added subscriber: @Harti

Added subscriber: @PratikPB2123

Guess the reported issue is duplicate of #81089 (Pointiness - wrong results with dense mesh and small scale)

Will merge into it. Thanks for the report

Closed as duplicate of #81089

Ok the bright dots are similar to the "#81089: Pointiness - wrong results with dense mesh and small scale" thread but the rectangular patterns are something else. I would like to have a dev to look over that issue.

Added subscriber: @JulianPerez

I can confirm this bug, when using the pointiness node at the highest resolution a line pattern becomes apparent

Here's the test file with a sphere with multires:
MultiresSphere.blend

Changed status from 'Duplicate' to: 'Needs Triage'

Added subscriber: @LeonardSiebeneicher

Here I removed Multires and put a fresh Multires.

The pattern only appears in areas I painted.

( Edit )

Now, Multires completely removed. Instead, there is a Subdivision modifier and a displacement noise.

Added subscriber: @JosephEagar

Adding a triangulate modifier seems to help. This may be due to how quads are internally triangulated only one way, which can result in funky behavior with high frequency details (the triangulate modifier by defaults picks the shortest diagonal). This is also why you often have to add a triangulate modifier to get normal maps to render correctly.

Odd. A triangulate modifier in 'fixed' mode also kind of helps, though there's a still a little bit of a pattern.

Changed status from 'Needs Triage' to: 'Confirmed'

Added subscriber: @leesonw

Changed status from 'Confirmed' to: 'Needs User Info'

I tested this on 2.83, 2.93 and 3.0 and it looks the same on all of them. Have you got an example of what I am suppose to see? and also if possible the version of blender this works on.

Have you got an example of what I am suppose to see?

I tried another screenshot which shows 'pointiness' artifacts. (Rendered viewport shading mode)

On the left side of the image, there are not many artifacts. But on the right side, pointiness node creates a lot of zig-zag artifacts. The artifacts are hard to see in thumbnail images. Seeing images in original scale helps.

To me it seems that the pointiness (zig-zag) artifact seems to depend on the frequency of slope changes on the surface.

Changed status from 'Needs User Info' to: 'Confirmed'

Added subscriber: @brecht

Changed status from 'Confirmed' to: 'Archived'

It's still fundamentally the same underlying problem as #81089 (Pointiness - wrong results with dense mesh and small scale), the pointiness implementation is really limited and looks at a small neighborhood. And triangulation does affect what that neighborhood is exactly.

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Multires results in a very funky "Pointiness" behaviour #90480