Rigid body simulation does not bake when using Python API to create and remove mesh data in frame_change_pre_handler #60136

New Issue

Ryan Guy · 2019-01-04T00:17:18+01:00

Ryan Guy commented

2019-01-04 00:17:18 +01:00

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

Blender Version
Broken: 2.80, 11f2c65128, 2019-01-03
Worked: 2.79b release

Short description of error

A rigid body simulation does not bake to completion when the frame_change_pre handler is used to create and then immediately remove a mesh data object. The simulation only bakes the first two frames and then stops.

Here is a short script that reproduces the issue:

import bpy

def frame_change_pre(scene):    
    new_mesh_data = bpy.data.meshes.new("mesh_name")
    bpy.data.meshes.remove(new_mesh_data)
    
bpy.app.handlers.frame_change_pre.append(frame_change_pre)

I have also reported another issue related to unexpected behavior when using the frame_change_pre handler here: blender/blender-addons#60094

Exact steps for others to reproduce the error

I have attached a .blend file that includes the script to reproduce this issue.

To reproduce:

Open the .blend file
Press 'Run Script'
Playback animation or attempt to bake the rigid body cache

To reproduce from a new .blend file:

Add default cube as a rigid body object
Run the script
Playback animation or attempt to bake the rigid body cache

rigid_body_bug.blend

**System Information** Operating system: Windows 10 Home Graphics card: GTX 1070 8GB **Blender Version** Broken: 2.80, 11f2c65128dc, 2019-01-03 Worked: 2.79b release **Short description of error** A rigid body simulation does not bake to completion when the **frame_change_pre** handler is used to create and then immediately remove a mesh data object. The simulation only bakes the first two frames and then stops. Here is a short script that reproduces the issue: ``` import bpy def frame_change_pre(scene): new_mesh_data = bpy.data.meshes.new("mesh_name") bpy.data.meshes.remove(new_mesh_data) bpy.app.handlers.frame_change_pre.append(frame_change_pre) ``` I have also reported another issue related to unexpected behavior when using the frame_change_pre handler here: blender/blender-addons#60094 **Exact steps for others to reproduce the error** I have attached a .blend file that includes the script to reproduce this issue. To reproduce: 1. Open the .blend file 2. Press 'Run Script' 3. Playback animation or attempt to bake the rigid body cache To reproduce from a new .blend file: 1. Add default cube as a rigid body object 2. Run the script 3. Playback animation or attempt to bake the rigid body cache [rigid_body_bug.blend](https://archive.blender.org/developer/F6165406/rigid_body_bug.blend)

Ryan Guy commented

2019-01-04 00:17:18 +01:00

Added subscriber: @rlguy

blender-admin commented

2019-01-04 00:17:18 +01:00

#60893 was marked as duplicate of this issue

blender-admin commented

2019-01-04 00:17:18 +01:00

#60919 was marked as duplicate of this issue

Campbell Barton was assigned by Sebastian Parborg

2019-01-25 12:09:11 +01:00

Sebastian Parborg commented

2019-01-29 12:18:10 +01:00

Added subscribers: @toxsickcity, @ZedDB

Sebastian Parborg commented

2019-01-29 17:52:01 +01:00

Added subscriber: @nacioss

Sebastian Parborg commented

2019-01-29 17:53:07 +01:00

Seems like frame_change_post is having issues as well.

Seems like `frame_change_post` is having issues as well.

Campbell Barton was unassigned by Brecht Van Lommel

2019-03-18 14:57:35 +01:00

Sergey Sharybin was assigned by Brecht Van Lommel

2019-03-18 14:57:35 +01:00

Brecht Van Lommel commented

2019-03-18 14:57:35 +01:00

Added subscriber: @ideasman42

Brecht Van Lommel commented

2019-03-18 15:01:11 +01:00

Added subscriber: @brecht

Brecht Van Lommel commented

2019-03-18 15:01:11 +01:00

This sounds like a dependency graph issue, and more of a design issue.

I did not investigate the file, but the dependency graph is intended to reset the physics caches when the scene is edited. This makes sense for user edits, but less so for scripts that change the scene in the frame change handler.

Maybe those should not be considered user edits. As mention in blender/blender-addons#60094, the design here should be clarified.

This sounds like a dependency graph issue, and more of a design issue. I did not investigate the file, but the dependency graph is intended to reset the physics caches when the scene is edited. This makes sense for user edits, but less so for scripts that change the scene in the frame change handler. Maybe those should not be considered user edits. As mention in blender/blender-addons#60094, the design here should be clarified.

André Savik commented

2019-05-05 01:48:52 +02:00

Added subscriber: @Klutz