Exporting procedural mesh animation with Alembic results in a crash #67627

New Issue

Ryan Guy · 2019-07-25T00:22:30+02:00

Ryan Guy commented

2019-07-25 00:22:30 +02:00

System Information
Operating system: Windows 10 Home
Graphics card: GTX 1070 8GB

Blender Version
Broken: 2.80, 4fe0fafb87, 2019-07-24
Worked: 2.79, 5bd8ac9, 2017-09-11

Short description of error

Exporting a procedural mesh to Alembic that is updated in the frame_change_pre handler results in a crash. This is an issue that is being encountered in the FLIP Fluids addon. I have created a small script that reproduces this issue.

The script and steps to reproduce this issue are similar to this report: #65816

import bpy

def frame_change_pre(scene):
    # A triangle that shifts in the z direction
    zshift = scene.frame_current * 0.1
    vertices = [(-1, -1, zshift), (1, -1, zshift), (0, 1, zshift)]
    triangles = [(0, 1, 2)]
    
    new_mesh_data = bpy.data.meshes.new("mesh_data" + str(scene.frame_current))
    new_mesh_data.from_pydata(vertices, [], triangles)
    
    mesh_cache = bpy.data.objects.get("mesh_cache")
    old_mesh_data = mesh_cache.data
    mesh_cache.data = new_mesh_data
    bpy.data.meshes.remove(old_mesh_data)
    
bpy.app.handlers.frame_change_pre.append(frame_change_pre)

This is the error output after the crash:

Read blend: C:\Users\ryanl\Downloads\procedural_alembic_export.blend
find_node component: Could not find ID MEmesh_data272
add_relation(Object Geometry Base Data) - Could not find op_from (ComponentKey(MEmesh_data272, GEOMETRY))
add_relation(Object Geometry Base Data) - Failed, but op_to (ComponentKey(OBmesh_cache, GEOMETRY)) was ok
find_node_operation: Failed for (PARAMETERS_ENTRY, '')
find_node_operation: Failed for (PARAMETERS_EVAL, '')
add_relation(Entry -> Eval) - Could not find op_from (OperationKey(type: PARAMETERS, component name: '', operation code: PARAMETERS_ENTRY))
add_relation(Entry -> Eval) - Could not find op_to (OperationKey(type: PARAMETERS, component name: '', operation code: PARAMETERS_EVAL))
find_node_operation: Failed for (PARAMETERS_EVAL, '')
find_node_operation: Failed for (PARAMETERS_EXIT, '')
add_relation(Entry -> Exit) - Could not find op_from (OperationKey(type: PARAMETERS, component name: '', operation code: PARAMETERS_EVAL))
add_relation(Entry -> Exit) - Could not find op_to (OperationKey(type: PARAMETERS, component name: '', operation code: PARAMETERS_EXIT))
find_node_operation: Failed for (GEOMETRY_EVAL, '')
find_node_operation: Failed for (GEOMETRY_EVAL_DONE, '')
add_relation(ObData Geom Eval Done) - Could not find op_from (OperationKey(type: GEOMETRY, component name: '', operation code: GEOMETRY_EVAL))
add_relation(ObData Geom Eval Done) - Could not find op_to (OperationKey(type: GEOMETRY, component name: '', operation code: GEOMETRY_EVAL_DONE))
find_node_operation: Failed for (GEOMETRY_SELECT_UPDATE, '')
add_relation(Data Selection -> Object Selection) - Could not find op_from (OperationKey(type: BATCH_CACHE, component name: '', operation code: GEOMETRY_SELECT_UPDATE))
add_relation(Data Selection -> Object Selection) - Failed, but op_to (OperationKey(type: BATCH_CACHE, component name: '', operation code: GEOMETRY_SELECT_UPDATE)) was ok
find_node_operation: Failed for (COPY_ON_WRITE, '')
add_relation(Eval Order) - Could not find op_from (OperationKey(type: COPY_ON_WRITE, component name: '', operation code: COPY_ON_WRITE))
add_relation(Eval Order) - Failed, but op_to (OperationKey(type: COPY_ON_WRITE, component name: '', operation code: COPY_ON_WRITE)) was ok
Error   : EXCEPTION_ACCESS_VIOLATION
Address : 0x00007FF70639C627
Error   : EXCEPTION_ACCESS_VIOLATION
Module  : C:\Users\ryanl\Downloads\blender-2.80.0-git.4fe0fafb8755-windows64\blender.exe

Sometimes the error output is this:

Read blend: C:\Users\ryanl\Downloads\procedural_alembic_export.blend
Error   : EXCEPTION_ACCESS_VIOLATION
Address : 0x00007FF70650CD40
Module  : C:\Users\ryanl\Downloads\blender-2.80.0-git.4fe0fafb8755-windows64\blender.exe

Exact steps for others to reproduce the error

I have attached a .blend file that will reproduce the issue.

procedural_alembic_export.blend

Open .blend file
Run the script

File > Export > Alembic

Blender does not crash 100% of the time. It seems that the chance of a crash occurring increases as the frame range increases. I have the end frame set to 2000, which results in a crash most of the time on my system.

**System Information** Operating system: Windows 10 Home Graphics card: GTX 1070 8GB **Blender Version** Broken: 2.80, 4fe0fafb8755, 2019-07-24 Worked: 2.79, 5bd8ac9, 2017-09-11 **Short description of error** Exporting a procedural mesh to Alembic that is updated in the frame_change_pre handler results in a crash. This is an issue that is being encountered in the FLIP Fluids addon. I have created a small script that reproduces this issue. The script and steps to reproduce this issue are similar to this report: #65816 ``` import bpy def frame_change_pre(scene): # A triangle that shifts in the z direction zshift = scene.frame_current * 0.1 vertices = [(-1, -1, zshift), (1, -1, zshift), (0, 1, zshift)] triangles = [(0, 1, 2)] new_mesh_data = bpy.data.meshes.new("mesh_data" + str(scene.frame_current)) new_mesh_data.from_pydata(vertices, [], triangles) mesh_cache = bpy.data.objects.get("mesh_cache") old_mesh_data = mesh_cache.data mesh_cache.data = new_mesh_data bpy.data.meshes.remove(old_mesh_data) bpy.app.handlers.frame_change_pre.append(frame_change_pre) ``` This is the error output after the crash: ``` Read blend: C:\Users\ryanl\Downloads\procedural_alembic_export.blend find_node component: Could not find ID MEmesh_data272 add_relation(Object Geometry Base Data) - Could not find op_from (ComponentKey(MEmesh_data272, GEOMETRY)) add_relation(Object Geometry Base Data) - Failed, but op_to (ComponentKey(OBmesh_cache, GEOMETRY)) was ok find_node_operation: Failed for (PARAMETERS_ENTRY, '') find_node_operation: Failed for (PARAMETERS_EVAL, '') add_relation(Entry -> Eval) - Could not find op_from (OperationKey(type: PARAMETERS, component name: '', operation code: PARAMETERS_ENTRY)) add_relation(Entry -> Eval) - Could not find op_to (OperationKey(type: PARAMETERS, component name: '', operation code: PARAMETERS_EVAL)) find_node_operation: Failed for (PARAMETERS_EVAL, '') find_node_operation: Failed for (PARAMETERS_EXIT, '') add_relation(Entry -> Exit) - Could not find op_from (OperationKey(type: PARAMETERS, component name: '', operation code: PARAMETERS_EVAL)) add_relation(Entry -> Exit) - Could not find op_to (OperationKey(type: PARAMETERS, component name: '', operation code: PARAMETERS_EXIT)) find_node_operation: Failed for (GEOMETRY_EVAL, '') find_node_operation: Failed for (GEOMETRY_EVAL_DONE, '') add_relation(ObData Geom Eval Done) - Could not find op_from (OperationKey(type: GEOMETRY, component name: '', operation code: GEOMETRY_EVAL)) add_relation(ObData Geom Eval Done) - Could not find op_to (OperationKey(type: GEOMETRY, component name: '', operation code: GEOMETRY_EVAL_DONE)) find_node_operation: Failed for (GEOMETRY_SELECT_UPDATE, '') add_relation(Data Selection -> Object Selection) - Could not find op_from (OperationKey(type: BATCH_CACHE, component name: '', operation code: GEOMETRY_SELECT_UPDATE)) add_relation(Data Selection -> Object Selection) - Failed, but op_to (OperationKey(type: BATCH_CACHE, component name: '', operation code: GEOMETRY_SELECT_UPDATE)) was ok find_node_operation: Failed for (COPY_ON_WRITE, '') add_relation(Eval Order) - Could not find op_from (OperationKey(type: COPY_ON_WRITE, component name: '', operation code: COPY_ON_WRITE)) add_relation(Eval Order) - Failed, but op_to (OperationKey(type: COPY_ON_WRITE, component name: '', operation code: COPY_ON_WRITE)) was ok Error : EXCEPTION_ACCESS_VIOLATION Address : 0x00007FF70639C627 Error : EXCEPTION_ACCESS_VIOLATION Module : C:\Users\ryanl\Downloads\blender-2.80.0-git.4fe0fafb8755-windows64\blender.exe ``` Sometimes the error output is this: ``` Read blend: C:\Users\ryanl\Downloads\procedural_alembic_export.blend Error : EXCEPTION_ACCESS_VIOLATION Address : 0x00007FF70650CD40 Module : C:\Users\ryanl\Downloads\blender-2.80.0-git.4fe0fafb8755-windows64\blender.exe ``` **Exact steps for others to reproduce the error** I have attached a .blend file that will reproduce the issue. [procedural_alembic_export.blend](https://archive.blender.org/developer/F7627291/procedural_alembic_export.blend) - Open .blend file - Run the script # File > Export > Alembic Blender does not crash 100% of the time. It seems that the chance of a crash occurring increases as the frame range increases. I have the end frame set to 2000, which results in a crash most of the time on my system.

Ryan Guy commented

2019-07-25 00:22:30 +02:00

Added subscriber: @rlguy

Juan Gea commented

2019-07-25 19:09:34 +02:00

Added subscribers: @dr.sybren, @juang3d

Juan Gea commented

2019-07-25 19:09:34 +02:00

Hey @dr.sybren what do you think about this?

It seems that @rlguy tried to use any of these handlers:

frame_change_pre
frame_change_post
render_pre
render_post

But it seems the crash is there with any of those.
I tried with your patch for the other bug but the crash is still present in this case.

Hey @dr.sybren what do you think about this? It seems that @rlguy tried to use any of these handlers: frame_change_pre frame_change_post render_pre render_post But it seems the crash is there with any of those. I tried with your patch for the other bug but the crash is still present in this case.

Ryan Guy commented

2019-07-25 19:38:25 +02:00

Note: render_pre and render_post handlers will not cause a crash in this issue since these are only called during render. I had tested the frame change and render handlers in issue blender/blender-addons#60094 which all resulted in a crash.

Note: *render_pre* and *render_post* handlers will not cause a crash in this issue since these are only called during render. I had tested the frame change and render handlers in issue blender/blender-addons#60094 which all resulted in a crash.

Sybren A. Stüvel self-assigned this 2019-07-30 10:49:32 +02:00

Sybren A. Stüvel commented

2019-07-30 11:36:56 +02:00

There are two things happening in the reported code:

The mesh object is replaced. This means the exporter is going to see it as a different mesh. Instead of having one mesh animated over time, you'll have a separate static mesh for every frame.
The changes in the data aren't seen by the export depsgraph, see blender/blender-addons#60094.

There are two things happening in the reported code: - The mesh object is replaced. This means the exporter is going to see it as a different mesh. Instead of having one mesh animated over time, you'll have a separate static mesh for every frame. - The changes in the data aren't seen by the export depsgraph, see blender/blender-addons#60094.

Sybren A. Stüvel commented

2019-07-31 12:30:17 +02:00

I've added a function (6d2f9b1dfa) to Blender that allows you to avoid replacing the mesh datablock. You can now write the code like this:

def frame_change_pre(scene):
    # A triangle that shifts in the z direction
    zshift = scene.frame_current * 0.1
    vertices = [(-1, -1, zshift), (1, -1, zshift), (0, 1, zshift)]
    triangles = [(0, 1, 2)]

    object = bpy.data.objects["The Object"]
    object.data.clear_geometry()
    object.data.from_pydata(vertices, [], triangles)

Note the new object.data.clear_geometry() function. This will erase all geometry from the mesh, and allow a subsequent from_pydata() call to fill it up again. It also just tags the mesh for geometry updates in the depsgraph; creating a new mesh datablock and deleting the old one will cause a complete rebuild of the relations in the depsgraph, which is more expensive.

The remaining part of this task is now the same as blender/blender-addons#60094, so I'll merge this task as a duplicate.

I've added a function (6d2f9b1dfa) to Blender that allows you to avoid replacing the mesh datablock. You can now write the code like this: ``` def frame_change_pre(scene): # A triangle that shifts in the z direction zshift = scene.frame_current * 0.1 vertices = [(-1, -1, zshift), (1, -1, zshift), (0, 1, zshift)] triangles = [(0, 1, 2)] object = bpy.data.objects["The Object"] object.data.clear_geometry() object.data.from_pydata(vertices, [], triangles) ``` Note the new `object.data.clear_geometry()` function. This will erase all geometry from the mesh, and allow a subsequent `from_pydata()` call to fill it up again. It also just tags the mesh for geometry updates in the depsgraph; creating a new mesh datablock and deleting the old one will cause a complete rebuild of the relations in the depsgraph, which is more expensive. The remaining part of this task is now the same as blender/blender-addons#60094, so I'll merge this task as a duplicate.

Sybren A. Stüvel commented

2019-07-31 12:31:12 +02:00

Closed as duplicate of blender/blender-addons#60094

Sybren A. Stüvel closed this issue

2019-07-31 12:31:12 +02:00

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Exporting procedural mesh animation with Alembic results in a crash #67627

File > Export > Alembic