Crash when turning on Keep Boundary #95542

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Gerstmann Bradley · 2022-02-05T23:28:21+01:00

Gerstmann Bradley commented

2022-02-05 23:28:21 +01:00

System Information
Operating system: Windows-10-10.0.17134-SP0 64 Bits
Graphics card: NVIDIA GeForce GTX 970M/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 466.11

Blender Version
Broken: version: 3.1.0 Beta, branch: master, commit date: 2022-02-04 20:19, hash: 0b4cf2984f
Worked: (newest version of Blender that worked as expected)

Short description of error
Here's the file, I can't simplify more.
It's a very specific and weird crash case. not sure really a bug or not.

Exact steps for others to reproduce the error
Open the file, toggle on the first Keep Boundary as shown.

Crash should happen Instantaneously.
CRASH1.blend
Simplified file:
CRASH1_simple.blend

**System Information** Operating system: Windows-10-10.0.17134-SP0 64 Bits Graphics card: NVIDIA GeForce GTX 970M/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 466.11 **Blender Version** Broken: version: 3.1.0 Beta, branch: master, commit date: 2022-02-04 20:19, hash: `0b4cf2984f` Worked: (newest version of Blender that worked as expected) **Short description of error** Here's the file, I can't simplify more. It's a very specific and weird crash case. not sure really a bug or not. **Exact steps for others to reproduce the error** Open the file, toggle on the first Keep Boundary as shown. ![image.png](https://archive.blender.org/developer/F12849216/image.png) Crash should happen Instantaneously. [CRASH1.blend](https://archive.blender.org/developer/F12849212/CRASH1.blend) Simplified file: [CRASH1_simple.blend](https://archive.blender.org/developer/F12855152/CRASH1_simple.blend)

Gerstmann Bradley commented

2022-02-05 23:28:21 +01:00

Added subscriber: @Bradley_G

Jesse Yurkovich commented

2022-02-05 23:49:14 +01:00

Added subscriber: @deadpin

Jesse Yurkovich commented

2022-02-05 23:49:14 +01:00

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

Jesse Yurkovich commented

2022-02-05 23:49:14 +01:00

Confirmed here. In debug builds it will hit the following assert:

BLI_assert failed: E:/source/blender-git/blender/source/blender/nodes/geometry/nodes/node_geo_dual_mesh.cc:452, sort_vertex_polys(), at 'j != connected_polygons.size()'

blender.exe!blender::nodes::node_geo_dual_mesh_cc::sort_vertex_polys(const Mesh & mesh, ... blender::MutableSpan<int> r_sorted_corners) Line 452	C++
blender.exe!blender::nodes::node_geo_dual_mesh_cc::calc_dual_mesh::__l2::<lambda>(blender::IndexRange range) Line 662	C++
blender.exe!blender::threading::parallel_for<void <lambda>(blender::IndexRange)>(blender::IndexRange range, __int64 grain_size, const blender::nodes::node_geo_dual_mesh_cc::calc_dual_mesh::__l2::void <lambda>(blender::IndexRange) & function) Line 83	C++
blender.exe!blender::nodes::node_geo_dual_mesh_cc::calc_dual_mesh(GeometrySet & geometry_set, const MeshComponent & in_component, const bool keep_boundaries) Line 645	C++
blender.exe!blender::nodes::node_geo_dual_mesh_cc::node_geo_exec::__l2::<lambda>(GeometrySet & geometry_set) Line 916	C++

Confirmed here. In debug builds it will hit the following assert: ``` BLI_assert failed: E:/source/blender-git/blender/source/blender/nodes/geometry/nodes/node_geo_dual_mesh.cc:452, sort_vertex_polys(), at 'j != connected_polygons.size()' blender.exe!blender::nodes::node_geo_dual_mesh_cc::sort_vertex_polys(const Mesh & mesh, ... blender::MutableSpan<int> r_sorted_corners) Line 452 C++ blender.exe!blender::nodes::node_geo_dual_mesh_cc::calc_dual_mesh::__l2::<lambda>(blender::IndexRange range) Line 662 C++ blender.exe!blender::threading::parallel_for<void <lambda>(blender::IndexRange)>(blender::IndexRange range, __int64 grain_size, const blender::nodes::node_geo_dual_mesh_cc::calc_dual_mesh::__l2::void <lambda>(blender::IndexRange) & function) Line 83 C++ blender.exe!blender::nodes::node_geo_dual_mesh_cc::calc_dual_mesh(GeometrySet & geometry_set, const MeshComponent & in_component, const bool keep_boundaries) Line 645 C++ blender.exe!blender::nodes::node_geo_dual_mesh_cc::node_geo_exec::__l2::<lambda>(GeometrySet & geometry_set) Line 916 C++ ```

Pratik Borhade commented

2022-02-06 02:22:11 +01:00

Added subscriber: @PratikPB2123

Jacques Lucke commented

2022-02-08 13:13:12 +01:00

Added subscribers: @wannes.malfait, @JacquesLucke

Jacques Lucke commented

2022-02-08 13:13:12 +01:00

The issue is probably that the Merge by Distance node produced fairly complex non-manifold geometry, that the dual mesh node does not handle correctly.
I simplified the file a bit and attached it to the report above.
@wannes.malfait can you have a look?

The issue is probably that the Merge by Distance node produced fairly complex non-manifold geometry, that the dual mesh node does not handle correctly. I simplified the file a bit and attached it to the report above. @wannes.malfait can you have a look?

Wannes Malfait commented

2022-02-08 13:45:01 +01:00

Yeah I saw this report and also tried simplifying it a little bit. I think the problem is that there are ngons which have more than 2 edges connected to a single vertex. I did not know that was possible. I tried creating the weirdest types of geometry for my tests, but apparently not weird enough. The current code assumes that each ngon has exactly 1 or 2 edges connected to a vertex, which causes the crash. The assert was there to ensure there was not some weird edge case that was missed for sorting, like this.

I'll try and take a look at it in the coming days. I'm afraid that there will be no "good" solution, either there will be some hole in the mesh, or the resulting dual ngon will have the vertices sorted badly.

In the mean time the best thing to do is add a triangulate node before the dual mesh which "solves" the problem.

Yeah I saw this report and also tried simplifying it a little bit. I think the problem is that there are ngons which have more than 2 edges connected to a single vertex. I did not know that was possible. I tried creating the weirdest types of geometry for my tests, but apparently not weird enough. The current code assumes that each ngon has exactly 1 or 2 edges connected to a vertex, which causes the crash. The assert was there to ensure there was not some weird edge case that was missed for sorting, like this. I'll try and take a look at it in the coming days. I'm afraid that there will be no "good" solution, either there will be some hole in the mesh, or the resulting dual ngon will have the vertices sorted badly. In the mean time the best thing to do is add a triangulate node before the dual mesh which "solves" the problem.

Jacques Lucke commented

2022-02-08 17:35:50 +01:00

I think the problem is that there are ngons which have more than 2 edges connected to a single vertex.

Hm, is that really the case? If yes, that sounds like it shouldn't be supported indeed and it may be a bug somewhere else. Doesn't that imply that an ngon has two corners at the same vertex?

> I think the problem is that there are ngons which have more than 2 edges connected to a single vertex. Hm, is that really the case? If yes, that sounds like it shouldn't be supported indeed and it may be a bug somewhere else. Doesn't that imply that an ngon has two corners at the same vertex?

Wannes Malfait commented

2022-02-09 18:15:36 +01:00

I have looked into it a little bit closer, and I have found the problem (or one of the problems). Basically the current code doesn't detect that the central vertex here is "non-manifold":

Then when it tries sorting all the polygon around that vertex it fails, because they can't be sorted. Don't know how easy it is to detect these kinds of vertices without something like the BMesh structure

I have looked into it a little bit closer, and I have found the problem (or one of the problems). Basically the current code doesn't detect that the central vertex here is "non-manifold": ![image.png](https://archive.blender.org/developer/F12857581/image.png) Then when it tries sorting all the polygon around that vertex it fails, because they can't be sorted. Don't know how easy it is to detect these kinds of vertices without something like the BMesh structure

Wannes Malfait self-assigned this 2022-02-09 19:25:20 +01:00

blender-admin commented

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

This issue was referenced by 82fc68ed90

This issue was referenced by 82fc68ed90bf1429579eddd5df14caf60b791b45

Hans Goudey commented

2022-02-18 18:36:38 +01:00

Changed status from 'Confirmed' to: 'Resolved'

Hans Goudey closed this issue

2022-02-18 18:36:38 +01:00

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Crash when turning on Keep Boundary #95542