6DOF Physics Constraint created in game engine is OK with X axis freedom but whizzes about all over the place with Y axis freedom #44738

New Issue

Jim Hawkins · 2015-05-17T10:29:50+02:00

Jim Hawkins commented

2015-05-17 10:29:50 +02:00

System Information
Same on the following:
Debian GNU/Linux 8 (jessie) 64-bit with Pegatron Radeon HD 6570
OS X 10.10.3 with Intel Iris Pro 1536 MB

Blender Version
Broken: version 2.74 (sub 0)

Short description of error
Constraint created with bge.constraints.createConstraint bge.constraints.GENERIC_6DOF_CONSTRAINT and then setParam(4, 1.0, 0.0) to give freedom in Y axis only creates a constraint that sometimes causes the attached object to whizz about in a crazy fashion when impulse is applied. It is OK with setParam(3, 1.0, 0.0) i.e. with freedom in X axis only.

Exact steps for others to reproduce the error
Sorry, this is a little lengthy but it's necessary to show the OK behaviour and the bug behaviour. The bug is demonstrated at step 10.
To run the demonstration:

Put the test01.blend and test01.py files in the same directory.
Open the test01.blend file in Blender and start the game engine.
The scene opens with one long object, the Origin, floating above a flatter

  object, the Floor.

Press space and a second long object, the Attachment, will appear and fall

  to the Floor. This is the no-constraint step. Press a cursor key and an
  impulse will be applied to the Attachment. The impulse is visualised by a
  temporary object. Different impulses are applied by pressing different
  cursor keys.

Press space again and the Attachment is deleted.
Press space again and the Attachment is added again, this time fixed by a

  constraint to the Origin. This is the no-freedom step. Pressing a cursor
  key will apply an impulse as in the no-constraint step, but it has no
  affect because of the constraint.

Press space again and the Attachment is deleted.
Press space again and the Attachment is added again, this time constrained

  with freedom to rotate around the X axis. This is the x-freedom step. The
  axis of the constraint is visualised for a short time when the Attachment
  is added. Pressing the cursor keys applies an impulse as before. It is
  possible to make the Attachment spin around and around.

Press space again and the Attachment is deleted.
Press space again and the Attachment is added again, this time constrained

  with freedom to rotate around the Y axis. This is the y-freedom step.
  Pressing the cursor keys applies an impulse as before. It should be
  possible to make the Attachment spin around, as it is in the x-freedom
  step, but there seems to be a bug. Small amounts of motion are OK, but if
  the Attachment reaches a further point of rotation, it whizzes about in
  all directions for a short time.

Press space again and the Attachment is deleted.
Either press Escape, to terminate the game engine, or press space again

  to resume at the no-constraint step.

test01.blend

test01.py

**System Information** Same on the following: Debian GNU/Linux 8 (jessie) 64-bit with Pegatron Radeon HD 6570 OS X 10.10.3 with Intel Iris Pro 1536 MB **Blender Version** Broken: version 2.74 (sub 0) **Short description of error** Constraint created with bge.constraints.createConstraint bge.constraints.GENERIC_6DOF_CONSTRAINT and then setParam(4, 1.0, 0.0) to give freedom in Y axis only creates a constraint that sometimes causes the attached object to whizz about in a crazy fashion when impulse is applied. It is OK with setParam(3, 1.0, 0.0) i.e. with freedom in X axis only. **Exact steps for others to reproduce the error** Sorry, this is a little lengthy but it's necessary to show the OK behaviour and the bug behaviour. The bug is demonstrated at step 10. To run the demonstration: 1. Put the test01.blend and test01.py files in the same directory. 2. Open the test01.blend file in Blender and start the game engine. 3. The scene opens with one long object, the Origin, floating above a flatter ``` object, the Floor. ``` 4. Press space and a second long object, the Attachment, will appear and fall ``` to the Floor. This is the no-constraint step. Press a cursor key and an impulse will be applied to the Attachment. The impulse is visualised by a temporary object. Different impulses are applied by pressing different cursor keys. ``` 5. Press space again and the Attachment is deleted. 6. Press space again and the Attachment is added again, this time fixed by a ``` constraint to the Origin. This is the no-freedom step. Pressing a cursor key will apply an impulse as in the no-constraint step, but it has no affect because of the constraint. ``` 7. Press space again and the Attachment is deleted. 8. Press space again and the Attachment is added again, this time constrained ``` with freedom to rotate around the X axis. This is the x-freedom step. The axis of the constraint is visualised for a short time when the Attachment is added. Pressing the cursor keys applies an impulse as before. It is possible to make the Attachment spin around and around. ``` 9. Press space again and the Attachment is deleted. 10. Press space again and the Attachment is added again, this time constrained ``` with freedom to rotate around the Y axis. This is the y-freedom step. Pressing the cursor keys applies an impulse as before. It should be possible to make the Attachment spin around, as it is in the x-freedom step, but there seems to be a bug. Small amounts of motion are OK, but if the Attachment reaches a further point of rotation, it whizzes about in all directions for a short time. ``` 11. Press space again and the Attachment is deleted. 12. Either press Escape, to terminate the game engine, or press space again ``` to resume at the no-constraint step. ``` [test01.blend](https://archive.blender.org/developer/F175715/test01.blend) [test01.py](https://archive.blender.org/developer/F175716/test01.py)

Jim Hawkins commented

2015-05-17 10:29:50 +02:00

Changed status to: 'Open'

Jim Hawkins commented

2015-05-17 10:29:50 +02:00

Added subscriber: @sjjh

Jorge Bernal commented

2015-05-17 17:02:16 +02:00

Changed status from 'Open' to: 'Archived'

Jorge Bernal closed this issue

2015-05-17 17:02:16 +02:00

Jorge Bernal self-assigned this 2015-05-17 17:02:16 +02:00

Jorge Bernal commented

2015-05-17 17:02:16 +02:00

It is a known limitation of our 6DOF constraint due to its euler nature. At Y axis unfortunately, once a joint exceeds +/-90 degrees, the constraint goes haywire.

See #42115 and http://bulletphysics.org/Bullet/phpBB3/viewtopic.php?f=9&t=8153

Sorry for the inconvenience.

Closing the report.

It is a known limitation of our 6DOF constraint due to its euler nature. At Y axis unfortunately, once a joint exceeds +/-90 degrees, the constraint goes haywire. See #42115 and http://bulletphysics.org/Bullet/phpBB3/viewtopic.php?f=9&t=8153 Sorry for the inconvenience. Closing the report.

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6DOF Physics Constraint created in game engine is OK with X axis freedom but whizzes about all over the place with Y axis freedom #44738