Retrieving evaluated mesh when realizing geometry nodes instances can fail #89905

New Issue

Simon Thommes · 2021-07-16T19:55:18+02:00

Simon Thommes commented

2021-07-16 19:55:18 +02:00

System Information
Operating system: Linux-5.11.0-7614-generic-x86_64-with-glibc2.32 64 Bits
Graphics card: Quadro RTX 6000/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 460.73.01

Blender Version
Broken: version: 3.0.0 Alpha, branch: master, commit date: 2021-07-16 07:47, hash: 038345fa56
Worked: Caused by {bfa3dc91b75407b063f2ac991b176d98c050f92d}

Short description of error
When realizing many instances from a collection info node, often many instances will fail to appear. It happens more often when there are more instances, and it depends on threading.
vertex_groups_evaluation_bug.mp4
vertex_group_evaluation_failure.blend

Exact steps for others to reproduce the error
Open sample file, enable viewport visibility of Plane object. Repeat.

Simpler example:
Toggle visibility for the "Points" object. Repeat until only some instances appear.
#89905 Reproduce.blend

**System Information** Operating system: Linux-5.11.0-7614-generic-x86_64-with-glibc2.32 64 Bits Graphics card: Quadro RTX 6000/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 460.73.01 **Blender Version** Broken: version: 3.0.0 Alpha, branch: master, commit date: 2021-07-16 07:47, hash: `038345fa56` Worked: Caused by {bfa3dc91b75407b063f2ac991b176d98c050f92d} **Short description of error** When realizing many instances from a collection info node, often many instances will fail to appear. It happens more often when there are more instances, and it depends on threading. [vertex_groups_evaluation_bug.mp4](https://archive.blender.org/developer/F10226050/vertex_groups_evaluation_bug.mp4) [vertex_group_evaluation_failure.blend](https://archive.blender.org/developer/F10226054/vertex_group_evaluation_failure.blend) **Exact steps for others to reproduce the error** Open sample file, enable viewport visibility of `Plane` object. Repeat. Simpler example: Toggle visibility for the "Points" object. Repeat until only some instances appear. [#89905 Reproduce.blend](https://archive.blender.org/developer/F10226249/T89905_Reproduce.blend)

Simon Thommes commented

2021-07-16 19:55:18 +02:00

Added subscriber: @SimonThommes

Hans Goudey commented

2021-07-16 20:35:12 +02:00

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

Hans Goudey self-assigned this 2021-07-16 20:35:12 +02:00

Hans Goudey commented

2021-07-16 22:17:07 +02:00

I've done a bit of investigation here. The problem seems to be a bit bigger than just the vertex groups, and I can also replicate it by realizing the instances before distribution.

Sometimes the mesh generated from joining the instances is smaller than other times:

New mesh size: 34680
New mesh size: 30923
New mesh size: 31790
New mesh size: 26010

It doesn't happen in a build without TBB (no threading).

This is quite odd, I'm not sure how the vertex refactor would cause this! I'll continue investigating later today.

I've done a bit of investigation here. The problem seems to be a bit bigger than just the vertex groups, and I can also replicate it by realizing the instances before distribution. Sometimes the mesh generated from joining the instances is smaller than other times: ![image.png](https://archive.blender.org/developer/F10226103/image.png) ``` New mesh size: 34680 New mesh size: 30923 New mesh size: 31790 New mesh size: 26010 ``` It doesn't happen in a build without TBB (no threading). This is quite odd, I'm not sure how the vertex refactor would cause this! I'll continue investigating later today.

Hans Goudey commented

2021-07-17 00:04:31 +02:00

Further investigation reveals that BKE_modifier_get_evaluated_mesh_from_evaluated_object sometimes returns NULL when gathering instances meshes to be realized.
I think I will bisect this just to make sure it's actually caused by the vertex group refactor.

Further investigation reveals that `BKE_modifier_get_evaluated_mesh_from_evaluated_object` sometimes returns NULL when gathering instances meshes to be realized. I think I will bisect this just to make sure it's actually caused by the vertex group refactor.

Hans Goudey commented

2021-07-17 02:02:02 +02:00

Bisecting finished, and it points to bfa3dc91b7

Honestly that makes a lot more sense based on the behavior I was observing when meshes are collected for instancing.

Bisecting finished, and it points to bfa3dc91b7 Honestly that makes a lot more sense based on the behavior I was observing when meshes are collected for instancing.

Hans Goudey changed title from ~~Vertex group evaluation failing on realized instances in geometry nodes~~ to Retrieving evaluated mesh when realizing geometry nodes instances can fail

2021-07-17 03:43:34 +02:00

Hans Goudey removed their assignment 2021-07-17 03:43:48 +02:00

Hans Goudey commented

2021-07-17 03:43:48 +02:00

Added subscriber: @HooglyBoogly