Rigid body Constraint: Generic are crazy for rotation along Y axis (Bullet issue?) #41809

New Issue

Piotr Załóg · 2014-09-13T11:56:25+02:00

Piotr Załóg commented

2014-09-13 11:56:25 +02:00

Windows 7 64

Blender 2.71 9337574

Every time when I use Generic Constraint and Object can rotate along Y axis, animation are crazy. Only Y axis is broken.

Open file. bug_generic_constraint_y.blend
Press Alt + A and see what will happen with green cube.

Not only I have this problem.

Windows 7 64 Blender 2.71 9337574 Every time when I use Generic Constraint and Object can rotate along Y axis, animation are crazy. Only Y axis is broken. 1. Open file. [bug_generic_constraint_y.blend](https://archive.blender.org/developer/F110094/bug_generic_constraint_y.blend) 2. Press Alt + A and see what will happen with green cube. Not only I have this problem.

Piotr Załóg commented

2014-09-13 11:56:25 +02:00

Changed status to: 'Open'

Piotr Załóg commented

2014-09-13 11:56:25 +02:00

Added subscriber: @piotr-14

Bastien Montagne changed title from ~~Rigid body Constraint: Generic are crazy~~ to Rigid body Constraint: Generic are crazy for rotation along Y axis (Bullet issue?)

2014-09-15 12:43:51 +02:00

Sergej Reich was assigned by Bastien Montagne

2014-09-15 12:43:51 +02:00

Bastien Montagne commented

2014-09-15 12:46:25 +02:00

Added subscriber: @mont29

Bastien Montagne commented

2014-09-15 12:46:25 +02:00

Confirmed.
From a quick print session, issue seems to happen in Bullet (at least, values gotten from RB_body_get_orientation() are first stable, with rotation along Y axis, and it soon starts to diverge to random axes...).

Sergej, you might know better! ;)

Confirmed. From a quick print session, issue seems to happen in Bullet (at least, values gotten from `RB_body_get_orientation()` are first stable, with rotation along Y axis, and it soon starts to diverge to random axes...). Sergej, you might know better! ;)

Lukas Tönne commented

2014-10-15 11:10:55 +02:00

Changed status from 'Open' to: 'Archived'

Lukas Tönne closed this issue

2014-10-15 11:10:55 +02:00

Lukas Tönne commented

2014-10-15 11:10:55 +02:00

Added subscriber: @LukasTonne

Lukas Tönne commented

2014-10-15 11:10:55 +02:00

The most plausible explanation i could find on this issue is that the 6dof constraint ("generic" in Blender terms) is based on Euler angles, which are prone to gimbal lock type issues. The ultimate solution would have to happen on the Bullet side as a quaternion-based 6dof constraint, but in the meantime you can use a true hinge constraint (which is more stable anyway) or just rotate the cube and use the x or z axis instead of y. See this thread for discussion:

http://bulletphysics.org/Bullet/phpBB3/viewtopic.php?t=8153

We can't really fix this on our side, so i'm archiving this report.

The most plausible explanation i could find on this issue is that the 6dof constraint ("generic" in Blender terms) is based on Euler angles, which are prone to gimbal lock type issues. The ultimate solution would have to happen on the Bullet side as a quaternion-based 6dof constraint, but in the meantime you can use a true hinge constraint (which is more stable anyway) or just rotate the cube and use the x or z axis instead of y. See this thread for discussion: http://bulletphysics.org/Bullet/phpBB3/viewtopic.php?t=8153 We can't really fix this on our side, so i'm archiving this report.

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Rigid body Constraint: Generic are crazy for rotation along Y axis (Bullet issue?) #41809