new_from_object crash with mesh DepsgraphObjectInstance.object created from non-mesh instance_object #120145

New Issue

Thomas Barlow · 2024-04-01T17:49:34+02:00

Thomas Barlow commented

2024-04-01 17:49:34 +02:00

System Information
Operating system: Windows-10-10.0.19045-SP0 64 Bits
Graphics card: NVIDIA GeForce GTX 1070 Ti/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 546.33

Blender Version
Broken: version: 4.2.0 Alpha, branch: main, commit date: 2024-03-31 11:47, hash: 4855f8cd9cbe
Worked: Never (these types of mesh instances appear to have first been available in 3.0, which also crashes)

Short description of error
Converting a mesh Object from a DepsgraphObjectInstance, whose instance_object is not a mesh, to a new mesh with bpy.data.meshes.new_from_object with preserve_all_data_layers=True crashes Blender.

Exact steps for others to reproduce the error
Note that CURVES objects which produce mesh geometry through Geometry Nodes such as Curve to Mesh also create a mesh object DepsgraphObjectInstance that crashes. The reproduction steps use a legacy CURVE object because the reproduction steps are simpler.

Delete all objects in the scene
Add>Curve>Bezier Curve
In the Object Data Properties, set the curve's Geometry>Bevel>Depth to 1m
Run the following script:

import bpy

C = bpy.context

dg = C.evaluated_depsgraph_get()

found = False

for instance in dg.object_instances:
    if instance.instance_object is not None and instance.instance_object.type != 'MESH':
        instance_mesh_object = instance.object
        if instance_mesh_object.type == 'MESH':
            found = True
            # No crash
            bpy.data.meshes.new_from_object(instance_mesh_object, preserve_all_data_layers=False, depsgraph=dg)
            # Crash!
            bpy.data.meshes.new_from_object(instance_mesh_object, preserve_all_data_layers=True, depsgraph=dg)
            break

if not found:
    raise RuntimeError("Could not find the mesh instance")

**System Information** Operating system: Windows-10-10.0.19045-SP0 64 Bits Graphics card: NVIDIA GeForce GTX 1070 Ti/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 546.33 **Blender Version** Broken: version: 4.2.0 Alpha, branch: main, commit date: 2024-03-31 11:47, hash: `4855f8cd9cbe` Worked: Never (these types of mesh instances appear to have first been available in 3.0, which also crashes) **Short description of error** Converting a mesh Object from a DepsgraphObjectInstance, whose `instance_object` is not a mesh, to a new mesh with `bpy.data.meshes.new_from_object` with `preserve_all_data_layers=True` crashes Blender. **Exact steps for others to reproduce the error** Note that `CURVES` objects which produce mesh geometry through Geometry Nodes such as `Curve to Mesh` also create a mesh object DepsgraphObjectInstance that crashes. The reproduction steps use a legacy `CURVE` object because the reproduction steps are simpler. 1) Delete all objects in the scene 2) Add>Curve>Bezier Curve 3) In the Object Data Properties, set the curve's Geometry>Bevel>Depth to 1m 4) Run the following script: ```py import bpy C = bpy.context dg = C.evaluated_depsgraph_get() found = False for instance in dg.object_instances: if instance.instance_object is not None and instance.instance_object.type != 'MESH': instance_mesh_object = instance.object if instance_mesh_object.type == 'MESH': found = True # No crash bpy.data.meshes.new_from_object(instance_mesh_object, preserve_all_data_layers=False, depsgraph=dg) # Crash! bpy.data.meshes.new_from_object(instance_mesh_object, preserve_all_data_layers=True, depsgraph=dg) break if not found: raise RuntimeError("Could not find the mesh instance") ```

blender.crash.txt

43 KiB

Thomas Barlow added the

labels 2024-04-01 17:49:35 +02:00

Thomas Barlow changed title from ~~bpy.data.meshes.new_from_object crash with mesh DepsgraphObjectInstance.object created from non-mesh instance_object~~ to new_from_object crash with mesh DepsgraphObjectInstance.object created from non-mesh instance_object

2024-04-01 17:50:36 +02:00

YimingWu commented

2024-04-02 07:22:07 +02:00

This happens due to mesh->corner_data->layers == null in sculpt_multires_modifier_get called with the instanced mesh object while trying to evaluate mesh modifiers to the final state.

Not sure if any CustomData::layers should be null at this stage and we can handle that in CustomData_get_active_layer_index, or it should not be null altogether. I'm leaning towards just a null pointer handling but not sure if it will break anything else. ~~Will try make a PR.~~

Looks like it will still break in subsequent places. Then the layers should not be null.

@HooglyBoogly interested in taking a look at this?

This happens due to `mesh->corner_data->layers == null` in `sculpt_multires_modifier_get` called with the instanced mesh object while trying to evaluate mesh modifiers to the final state. Not sure if any `CustomData::layers` should be `null` at this stage and we can handle that in `CustomData_get_active_layer_index`, or it should not be null altogether. I'm leaning towards just a null pointer handling but not sure if it will break anything else. <s>Will try make a PR.</s> Looks like it will still break in subsequent places. Then the `layers` should not be null. @HooglyBoogly interested in taking a look at this?

YimingWu added

and removed

labels 2024-04-02 07:22:32 +02:00

Philipp Oeser commented

2024-04-03 14:49:19 +02:00

Prefer if crashes are set to High priority (could of course be lowered again if considered not severe enough)