Rigid body joint object doesn't hold position #18874

New Issue

Dolf Veenvliet · 2009-06-02T23:59:40+02:00

Dolf Veenvliet commented

2009-06-02 23:59:40 +02:00

Group: V 2.49 release
Resolution: Rejected
Category: Game engine

%%%Right... easiest is if you just look in the attached file.

Skip a frame ahead (from frame 1 to frame 2). You can clearly see that the object centre of the selected object moves relative to the active object.

I'm just using a basic ball joint here, but it does it in the new mode as well.

I thought it was an issue with the size of the objects. But if I resize them, apply the size... it "appears" fixed... but it isn't. It's just not as apparent.

It's quite clear if you put an empty that's the child of "Cube", at the position of "Cube.001".

I tried to find the exact cause, thought it didn't happen in 2.48, but it seems like it does it there as well.

If it's just a generic math precision issue and not a bug, I'm sorry.%%%

**Group**: V 2.49 release **Resolution**: Rejected **Category**: Game engine %%%Right... easiest is if you just look in the attached file. Skip a frame ahead (from frame 1 to frame 2). You can clearly see that the object centre of the selected object moves relative to the active object. I'm just using a basic ball joint here, but it does it in the new mode as well. I thought it was an issue with the size of the objects. But if I resize them, apply the size... it "appears" fixed... but it isn't. It's just not as apparent. It's quite clear if you put an empty that's the child of "Cube", at the position of "Cube.001". I tried to find the exact cause, thought it didn't happen in 2.48, but it seems like it does it there as well. If it's just a generic math precision issue and not a bug, I'm sorry.%%%

Dolf Veenvliet commented

2009-06-02 23:59:40 +02:00

Changed status to: 'Open'

Nobody commented

2009-06-02 23:59:40 +02:00

This task was automatically closed as archived as part of migration, because the project or tracker this task belonged to is no longer active.

Dolf Veenvliet commented

2009-06-03 00:01:54 +02:00

%%%Oh.. the ipos are recorded with the game engine... I am not 100% sure if it's the recorded ipos, or it happens in the GE itself, hard to tell at the high frame rates.%%%

Brecht Van Lommel commented

2009-06-09 20:56:09 +02:00

%%%If you disable the Record Game Ipo option, and lower gravity, the same behavior can be seen in the game engine, so I guess it happens in the physics simulation itself. No idea what the limits are of this feature though, so assigning to Erwin.%%%

Erwin Coumans commented

2009-06-11 15:23:11 +02:00

%%%It is easy to break rigid body dynamics systems, to prevent this:

See for some tips here:
http://www.bulletphysics.com/mediawiki-1.5.8/index.php?title=Physics_Tips
Please first experiment with working rigid body examples, use the game engine regression test files, from the Blender download page.

Thanks,
Erwin
%%%

%%%It is easy to break rigid body dynamics systems, to prevent this: 1) See for some tips here: http://www.bulletphysics.com/mediawiki-1.5.8/index.php?title=Physics_Tips 2) Please first experiment with working rigid body examples, use the game engine regression test files, from the Blender download page. Thanks, Erwin %%%

Erwin Coumans commented

2009-06-11 15:23:33 +02:00

Changed status from 'Open' to: 'Archived'

Erwin Coumans closed this issue

2009-06-11 15:23:33 +02:00

Dolf Veenvliet commented

2009-06-11 16:46:27 +02:00

%%%But... how can it be that an object centre moves relative to a "parent"... that ought to simply never happen. I'd rather have inaccuracy in the rotation of the child than having it "move" relative to it's parent.

And not directly this issue perhaps, but if 1 blender unit is 1 meter... isn't 0.2 units a bit of a narrow margin? if you have a character with fingers and toes and such in a ragdoll, by definition all of those will be smaller than 200cm... quite a bit smaller. And I'd consider that a common situation.%%%

%%%But... how can it be that an object centre moves relative to a "parent"... that ought to simply never happen. I'd rather have inaccuracy in the rotation of the child than having it "move" relative to it's parent. And not directly this issue perhaps, but if 1 blender unit is 1 meter... isn't 0.2 units a bit of a narrow margin? if you have a character with fingers and toes and such in a ragdoll, by definition all of those will be smaller than 200cm... quite a bit smaller. And I'd consider that a common situation.%%%

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Rigid body joint object doesn't hold position #18874