Render crash when an object is updated with a frame_change_post handler while another object's Show in Render property is keyframed #76422

New Issue

Ryan Guy · 2020-05-04T23:49:04+02:00

Ryan Guy commented

2020-05-04 23:49:04 +02:00

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

Blender Version
Broken: Blender 2.90 Alpha, fdebdfa320

Short description of error

This bug was reported to us while developing the FLIP Fluids addon. I have reduced the bug to a simple .blend file and script that can reproduce the issue.

I have an object in my scene that is procedurally updated using the frame_change_post handler with the following script:

import bpy

def frame_change_post(scene, depsgraph):
    # Generate a 2d grid of vertices
    vertices = []
    for j in range(100):
        for i in range(100):
            vertices.append((i * 0.05, j * 0.05, 0.1 * scene.frame_current))
    
    mesh_cache_object = bpy.data.objects.get("MeshCache")
    mesh_cache_object.data.clear_geometry()
    mesh_cache_object.data.from_pydata(vertices, [], [])
    depsgraph.update()
    
bpy.app.handlers.frame_change_post.append(frame_change_post)

I have another object in my scene that is a regular Cube object. This object has the Show in Renders property keyframed from Enabled to Disabled.

When I run the script and render an image or animation, Blender crashes with the following crash report:

bug_report.crash.txt

Additional notes:

The crash can be prevented by clearing the Show in Renders keyframes
The crash can be prevented by disabling Motion Blur in the Cycles Render Properties
The Lock Interface option is enabled, which is recommented to prevent render thread conflicts

Exact steps for others to reproduce the error

Attached is a .blend file that can reproduce the issue:

bug_report.blend

Open .blend file
Run the script
Render > Render Image

Blender crashes

**System Information** Operating system: Windows 10 Home Graphics card: GTX 1070 8GB **Blender Version** Broken: Blender 2.90 Alpha, fdebdfa320ec **Short description of error** This bug was reported to us while developing the FLIP Fluids addon. I have reduced the bug to a simple .blend file and script that can reproduce the issue. I have an object in my scene that is procedurally updated using the **frame_change_post** handler with the following script: ``` import bpy def frame_change_post(scene, depsgraph): # Generate a 2d grid of vertices vertices = [] for j in range(100): for i in range(100): vertices.append((i * 0.05, j * 0.05, 0.1 * scene.frame_current)) mesh_cache_object = bpy.data.objects.get("MeshCache") mesh_cache_object.data.clear_geometry() mesh_cache_object.data.from_pydata(vertices, [], []) depsgraph.update() bpy.app.handlers.frame_change_post.append(frame_change_post) ``` I have another object in my scene that is a regular Cube object. This object has the **Show in Renders** property keyframed from Enabled to Disabled. When I run the script and render an image or animation, Blender crashes with the following crash report: [bug_report.crash.txt](https://archive.blender.org/developer/F8512719/bug_report.crash.txt) Additional notes: - The crash can be prevented by clearing the Show in Renders keyframes - The crash can be prevented by disabling Motion Blur in the Cycles Render Properties - The Lock Interface option is enabled, which is recommented to prevent render thread conflicts **Exact steps for others to reproduce the error** Attached is a .blend file that can reproduce the issue: [bug_report.blend](https://archive.blender.org/developer/F8512726/bug_report.blend) 1. Open .blend file 2. Run the script 3. Render > Render Image Blender crashes

Ryan Guy commented

2020-05-04 23:49:04 +02:00

Added subscriber: @rlguy

Evan Wilson commented

2020-05-05 00:51:01 +02:00

Added subscriber: @EAW

Evan Wilson commented

2020-05-05 00:51:01 +02:00

Trying to render in a debug build leads to:

**current_exception** was nullptr. occurred```

```blender.exe!BLI_system_backtrace(_iobuf * fp=0x00007ffbb1dafcb0) Line 353
	at C:\blender-git\blender\source\blender\blenlib\intern\system_win32.c(353)

Lines 349-353

{
  SymInitialize(GetCurrentProcess(), NULL, TRUE);
  bli_load_symbols();
  bli_windows_system_backtrace_exception_record(fp, current_exception->ExceptionRecord);

Just before that:

	at C:\blender-git\blender\source\blender\blenkernel\intern\object_update.c(453)

Lines 442-453

                                     Scene *scene,
                                     const int view_layer_index,
                                     Object *object,
                                     int base_index,
                                     const bool is_from_set)
{
  /* TODO(sergey): Avoid list lookup. */
  BLI_assert(view_layer_index >= 0);
  ViewLayer *view_layer = BLI_findlink(&scene->view_layers, view_layer_index);
  BLI_assert(view_layer != NULL);
  BLI_assert(view_layer->object_bases_array != NULL);```

__Trying to render in a debug build leads to:__ ```Exception thrown: read access violation. **current_exception** was nullptr. occurred``` ```blender.exe!BLI_system_backtrace(_iobuf * fp=0x00007ffbb1dafcb0) Line 353 at C:\blender-git\blender\source\blender\blenlib\intern\system_win32.c(353) ``` Lines 349-353 ```void BLI_system_backtrace(FILE *fp) { SymInitialize(GetCurrentProcess(), NULL, TRUE); bli_load_symbols(); bli_windows_system_backtrace_exception_record(fp, current_exception->ExceptionRecord); ``` __Just before that:__ ```blender.exe!BKE_object_eval_eval_base_flags(Depsgraph * depsgraph=0x0000027fe54e9e78, Scene * scene=0x0000027fe7600428, const int view_layer_index=0, Object * object=0x0000027ff24a02e8, int base_index=2, const bool is_from_set=false) Line 453 at C:\blender-git\blender\source\blender\blenkernel\intern\object_update.c(453) ``` Lines 442-453 ```void BKE_object_eval_eval_base_flags(Depsgraph *depsgraph, Scene *scene, const int view_layer_index, Object *object, int base_index, const bool is_from_set) { /* TODO(sergey): Avoid list lookup. */ BLI_assert(view_layer_index >= 0); ViewLayer *view_layer = BLI_findlink(&scene->view_layers, view_layer_index); BLI_assert(view_layer != NULL); BLI_assert(view_layer->object_bases_array != NULL);```

Germano Cavalcante commented

2020-05-05 14:48:16 +02:00

Added subscriber: @mano-wii

Germano Cavalcante commented

2020-05-05 14:48:16 +02:00

Seems to be related to #71908

Sybren A. Stüvel commented

2020-05-07 10:51:53 +02:00

Added subscriber: @dr.sybren

Sybren A. Stüvel commented

2020-05-07 10:51:53 +02:00

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

Sybren A. Stüvel closed this issue

2020-05-07 10:51:53 +02:00

Sybren A. Stüvel self-assigned this 2020-05-07 10:51:53 +02:00

Sybren A. Stüvel commented

2020-05-07 10:51:53 +02:00

@mano-wii is right, it's exactly the same script as in #71908, but with a different issue.

The crash is avoided when you remove the depsgraph.update() call. This call is also not necessary, which can be actually seen when you add a face to the mesh so that it can be rendered:

import bpy

def frame_change_post(scene, depsgraph):
    # Generate a triangle
    z = scene.frame_current / 10
    vertices = [
        (0, 0, z),
        (1, 0, z),
        (0, 1, z),
    ]
    faces = [(0, 1, 2)]
    
    mesh_cache_object = bpy.data.objects.get("MeshCache")
    mesh_cache_object.data.clear_geometry()
    mesh_cache_object.data.from_pydata(vertices, [], faces)

bpy.app.handlers.frame_change_post.append(frame_change_post)

As changing the frame is done in a way that requires a certain state of the depsgraph, and forcing an update from Python like this disregards that, I don't see how calling depsgraph.update() here could be supported.

@mano-wii is right, it's exactly the same script as in #71908, but with a different issue. The crash is avoided when you remove the `depsgraph.update()` call. This call is also not necessary, which can be actually seen when you add a face to the mesh so that it can be rendered: ``` import bpy def frame_change_post(scene, depsgraph): # Generate a triangle z = scene.frame_current / 10 vertices = [ (0, 0, z), (1, 0, z), (0, 1, z), ] faces = [(0, 1, 2)] mesh_cache_object = bpy.data.objects.get("MeshCache") mesh_cache_object.data.clear_geometry() mesh_cache_object.data.from_pydata(vertices, [], faces) bpy.app.handlers.frame_change_post.append(frame_change_post) ``` As changing the frame is done in a way that requires a certain state of the depsgraph, and forcing an update from Python like this disregards that, I don't see how calling `depsgraph.update()` here could be supported.

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Render crash when an object is updated with a frame_change_post handler while another object's Show in Render property is keyframed #76422