Wrong Motion Blur with Rigid Body Simulation / Point Cache #40017

New Issue

Kai Kostack · 2014-05-04T03:01:25+02:00

Kai Kostack commented

2014-05-04 03:01:25 +02:00

System Information
Windows 7 x64 and Linux

Blender Version
Broken: Probably with introduction of deformation motion blur.

Short description of error
Motion blur together with rigid body simulation produces wrong and arbitrary blurred images.

Exact steps for others to reproduce the error

A .blend file is attached with a cube as test rigid body and motion blur enabled.

Step a few frames forward to generate some simulation data and motion
Click "Deformation" checkbox in motion blur panel
Render image, again and again and again... see the differences. Some extreme renders are attached here.
Notice also that the rigid body continues the simulation one frame at a time although you're rerendering the same frame

cube_bugtest.blend

**System Information** Windows 7 x64 and Linux **Blender Version** Broken: Probably with introduction of deformation motion blur. **Short description of error** Motion blur together with rigid body simulation produces wrong and arbitrary blurred images. **Exact steps for others to reproduce the error** A .blend file is attached with a cube as test rigid body and motion blur enabled. 1. Step a few frames forward to generate some simulation data and motion 2. Click "Deformation" checkbox in motion blur panel 3. Render image, again and again and again... see the differences. Some extreme renders are attached here. 4. Notice also that the rigid body continues the simulation one frame at a time although you're rerendering the same frame [cube_bugtest.blend](https://archive.blender.org/developer/F86841/cube_bugtest.blend) ![sample1.png](https://archive.blender.org/developer/F86842/sample1.png) ![sample3.png](https://archive.blender.org/developer/F86844/sample3.png) ![sample4.png](https://archive.blender.org/developer/F86843/sample4.png) ![sample2.png](https://archive.blender.org/developer/F86845/sample2.png)

Kai Kostack commented

2014-05-04 03:01:25 +02:00

Changed status to: 'Open'

Kai Kostack commented

2014-05-04 03:01:25 +02:00

Added subscriber: @KaiKostack-3

blender-admin commented

2014-05-04 03:01:25 +02:00

#41654 was marked as duplicate of this issue

Martin Felke commented

2014-05-04 11:27:58 +02:00

Added subscriber: @scorpion81

Martin Felke commented

2014-05-04 11:27:58 +02:00

Hi,

i have been drilling down to pointcache.c regarding to this bug.... seems to be an one-liner.

in

static void ptcache_rigidbody_interpolate(int index, void *rb_v, void **data, float cfra, float cfra1, float cfra2, float *old_data)

replace the call to

psys_interpolate_particle(-1, keys, (cfra - cfra1) / dfra, keys, 1);

by

interp_v3_v3v3(keys->co, keys[1].co, keys[2].co, (cfra - cfra1) / dfra);

That fixed it for me under linux and windows... in my fracture branch. Just a suggestion where to look at.

Hi, i have been drilling down to pointcache.c regarding to this bug.... seems to be an one-liner. in ``` static void ptcache_rigidbody_interpolate(int index, void *rb_v, void **data, float cfra, float cfra1, float cfra2, float *old_data) ``` replace the call to ``` psys_interpolate_particle(-1, keys, (cfra - cfra1) / dfra, keys, 1); ``` by ``` interp_v3_v3v3(keys->co, keys[1].co, keys[2].co, (cfra - cfra1) / dfra); ``` That fixed it for me under linux and windows... in my fracture branch. Just a suggestion where to look at.

Kai Kostack commented

2014-05-04 12:52:44 +02:00

Tested on Windows. Works in part but the simulation still continues on rerendering and then produces still artifacts.

It's important that you check the motion blur checkbox in the object properties once beforehand, because this somehow triggers the effect.

Good start though.

Tested on Windows. Works in part but the simulation still continues on rerendering and then produces still artifacts. It's important that you check the motion blur checkbox in the object properties once beforehand, because this somehow triggers the effect. Good start though.

Sergej Reich was assigned by Brecht Van Lommel

2014-05-06 14:42:32 +02:00

Brecht Van Lommel commented

2014-05-06 14:42:32 +02:00

Added subscriber: @brecht

Brecht Van Lommel commented

2014-05-06 14:42:32 +02:00

Ok, this doesn't seem to be related to deformation motion blur, for example changing the Pass Index, or using Blender Internal has the same problem. What I guess happens is that changing any object property causes a dependency graph update, which then somehow causes problems with the rigid body cache.

The usage of psys_interpolate_particle is indeed a problem because the velocity in ParticleKey is used but not initialized for the old_data case.

Generally for rendering with motion blur, the simulation should be baked in advance.

Ok, this doesn't seem to be related to deformation motion blur, for example changing the Pass Index, or using Blender Internal has the same problem. What I guess happens is that changing any object property causes a dependency graph update, which then somehow causes problems with the rigid body cache. The usage of `psys_interpolate_particle` is indeed a problem because the velocity in `ParticleKey` is used but not initialized for the `old_data` case. Generally for rendering with motion blur, the simulation should be baked in advance.

Jonathan Lampel commented

2014-08-20 19:01:39 +02:00

Added subscriber: @JonathanLampel-4

Jonathan Lampel commented

2014-08-20 19:26:51 +02:00

I am running into the same issue, and my simulation was baked in advance before using motion blur. Everything worked fine for a while, but it decided to act up today. Is there any way to workaround this?

I am running into the same issue, and my simulation was baked in advance before using motion blur. Everything worked fine for a while, but it decided to act up today. Is there any way to workaround this? ![Motion_Blur_Bug.jpg](https://archive.blender.org/developer/F105520/Motion_Blur_Bug.jpg)

Kai Kostack commented

2014-08-20 20:08:25 +02:00

Looks like the bug is back. I can confirm that my test blend file doesn't work anymore, too. The cube disappears completely now despite a fully baked simulation.

Tested with Blender 2.71 for Win64, Hash: 9337574

Looks like the bug is back. I can confirm that my test blend file doesn't work anymore, too. The cube disappears completely now despite a fully baked simulation. Tested with Blender 2.71 for Win64, Hash: 9337574

Sergej Reich commented

2014-08-27 20:00:28 +02:00

Can't reproduce issues with baked sim with either 2.71 or master. Are there specific steps I can follow?

Kai Kostack commented

2014-08-27 20:53:52 +02:00

No specific steps, load the cube_bugtest.blend into Blender and render animation (baking is optional). After the first frame the result should look like one of the wrong examples above.

When in doubt if there's a bug, try on windows.

No specific steps, load the cube_bugtest.blend into Blender and render animation (baking is optional). After the first frame the result should look like one of the wrong examples above. When in doubt if there's a bug, try on windows.

Sergej Reich commented

2014-08-27 21:31:32 +02:00

Ok, can reproduce now.

Sergey Sharybin commented

2014-09-08 12:18:52 +02:00

Added subscribers: @gandalf3, @KevinMossey, @ThomasDinges, @Sergey

Sergey Sharybin commented

2014-09-08 12:18:52 +02:00

◀ Merged tasks: #41654.

gandalf3 commented

2014-09-09 00:48:33 +02:00

I've managed to reproduce this too, with a simulation baked from the scene panel in 2.71 (It's inconsistent though, attempting to do it in a fresh file failed).
The exact same file/cache renders correctly in 2.69.

I've managed to reproduce this too, with a simulation baked from the scene panel in 2.71 (It's inconsistent though, attempting to do it in a fresh file failed). The exact same file/cache renders correctly in 2.69.

gandalf3 commented

2014-09-30 19:43:09 +02:00

This bug is still present in 2.72 RC1. The exact same file/cache appears fine in 2.70 as well as 2.69.

Sen Haerens commented

2014-10-01 10:38:37 +02:00

Added subscriber: @SenHaerens

Maverick commented

2014-10-02 13:57:35 +02:00

Added subscriber: @dragostanasie

Maverick commented

2014-10-02 13:57:35 +02:00

Confirmed on 2.72 (0334be9)

The cube is either transparent or completely disappears.

Confirmed on 2.72 (0334be9) The cube is either transparent or completely disappears.

gandalf3 commented

2014-10-12 02:56:22 +02:00

This bug is still here in 95182d1, (2.72).
Enabling deformation motion blur doesn't seem necessary to reproduce the issue.

Not to complain or anything, but this makes it impossible to render rigid bodies with motion blur in 2.71+, which means that it's necessary to revert to 2.70 to render rigid body sims.
This makes it difficult and awkward to render anything with rigid bodies and newer features like volumetrics.

Any chance of this getting fixed by 2.73?

This bug is still here in 95182d1, (2.72). Enabling deformation motion blur doesn't seem necessary to reproduce the issue. Not to complain or anything, but this makes it impossible to render rigid bodies with motion blur in 2.71+, which means that it's necessary to revert to 2.70 to render rigid body sims. This makes it difficult and awkward to render anything with rigid bodies and newer features like volumetrics. Any chance of this getting fixed by 2.73?

Maverick commented

2014-10-12 21:33:42 +02:00

I feel you brother !
..however Cycles no longer has a dedicated core developer and this is not an easy task to fix.
Dark days are coming.

I feel you brother ! ..however Cycles no longer has a dedicated core developer and this is not an easy task to fix. Dark days are coming.

Thomas Dinges commented

2014-10-22 21:19:23 +02:00

This is not a Cycles bug as mentioned by Brecht and Sergey in this and the merged report. ;)