Random per Island splits mesh based on sharp edges #95619

New Issue

slowburn · 2022-02-08T18:16:35+01:00

slowburn commented

2022-02-08 18:16:35 +01:00

System Information
Operating system: Windows-10-10.0.19043-SP0 64 Bits
Graphics card: NVIDIA GeForce RTX 3060 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 497.09

Blender Version
Broken: version: 3.1.0 Beta, branch: master, commit date: 2022-02-07 22:08, hash: 229d0ace02
Worked: not sure

Short description of error
If a contiguous mesh island is split into different parts by sharp edges, Random per Island input will treat those parts as separate mesh islands. Sharp edges can be set manually or with an Auto Smooth angle setting in object data properties. Also Shade Smooth has to be enabled.

Exact steps for others to reproduce the error

Open example file
Switch to Cycles viewport shading
Reduce Auto Smooth angle until 2 bent planes get split into different parts.
RandomperIsland_test.blend

**System Information** Operating system: Windows-10-10.0.19043-SP0 64 Bits Graphics card: NVIDIA GeForce RTX 3060 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 497.09 **Blender Version** Broken: version: 3.1.0 Beta, branch: master, commit date: 2022-02-07 22:08, hash: `229d0ace02` Worked: not sure **Short description of error** If a contiguous mesh island is split into different parts by sharp edges, Random per Island input will treat those parts as separate mesh islands. Sharp edges can be set manually or with an Auto Smooth angle setting in object data properties. Also Shade Smooth has to be enabled. ![rand_per_island.jpg](https://archive.blender.org/developer/F12855539/rand_per_island.jpg) ![rand_per_island2.jpg](https://archive.blender.org/developer/F12855541/rand_per_island2.jpg) **Exact steps for others to reproduce the error** - Open example file - Switch to Cycles viewport shading - Reduce Auto Smooth angle until 2 bent planes get split into different parts. [RandomperIsland_test.blend](https://archive.blender.org/developer/F12855548/RandomperIsland_test.blend)

slowburn commented

2022-02-08 18:16:35 +01:00

Added subscriber: @slowburn

Pratik Borhade commented

2022-02-09 03:33:05 +01:00

Added subscriber: @PratikPB2123

Pratik Borhade commented

2022-02-09 03:33:05 +01:00

Probably similar to this report: #92886 (Curve to Mesh node causes other objects to edge split when not shaded smooth)
I will mark this as duplicate. Thanks for the report!

Probably similar to this report: #92886 (Curve to Mesh node causes other objects to edge split when not shaded smooth) I will mark this as duplicate. Thanks for the report!

Pratik Borhade commented

2022-02-09 03:54:43 +01:00

Closed as duplicate of #92886

Pratik Borhade closed this issue

2022-02-09 03:54:43 +01:00

Hans Goudey commented

2022-02-09 22:38:50 +01:00

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

Hans Goudey reopened this issue

2022-02-09 22:38:50 +01:00

Hans Goudey commented

2022-02-09 22:44:50 +01:00

Added subscriber: @HooglyBoogly

Hans Goudey commented

2022-02-09 22:44:50 +01:00

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

Hans Goudey commented

2022-02-09 22:44:50 +01:00

I expect this is because of the way Cycles currently calculates sharp normals:

    if (mesh.use_auto_smooth()) {
      mesh.split_faces(false);
    }

That seems very far from ideal, it should be using the face corner normals instead. But maybe there's a good reason to do it this way, I'm not sure.

I expect this is because of the way Cycles currently calculates sharp normals: ``` if (mesh.use_auto_smooth()) { mesh.split_faces(false); } ``` That seems very far from ideal, it should be using the face corner normals instead. But maybe there's a good reason to do it this way, I'm not sure.

Pratik Borhade commented

2022-02-10 01:39:00 +01:00

Sorry @HooglyBoogly for merging the report