Page 1 of 1

strength of grabbing 6dof Constraint

Posted: Thu Aug 14, 2014 9:03 am
by Moose

I could use a little advice on a problem I'm having with a generic 6dof. Basically, I am using this constraint as picking cursor, much like the demos use point to point. Can can however not use point to point as my picking constraint also needs to rotate the object because this is in an immersive VR environment and often used with 3d mice and such equipment. Long story short, when my user moves this constraint about, the object gravitates towards it and also follows the movement and rotation. Much like intended.

The problem occurs when the user stops moving in mid air. What I want is the object to hold it's position at the constraint until I disable it (the user releases the input devices button).
What happens instead is, that gravity kicks in and the object starts to fall to the ground. (also with small gravity values). Then, as soon as the constraint moves again, even a tiny bit, the constraint seems to suddenly become active again and violently pulls the object that now lies on the ground towards it. The force appears to be so strong that the object "shoots" right through the constraint and from that point on moves erratically throw space until finally I release the constraint.

Now how can I tackle this? Are the parameters that need tweaking?
The ones that I currently set are:

generic_constraint->setParam(BT_CONSTRAINT_STOP_CFM, 0.8, 0); // default 0.0f
generic_constraint->setParam(BT_CONSTRAINT_STOP_CFM, 0.8, 1);
generic_constraint->setParam(BT_CONSTRAINT_STOP_CFM, 0.8, 2);
generic_constraint->setParam(BT_CONSTRAINT_STOP_CFM, 0.8, 3);
generic_constraint->setParam(BT_CONSTRAINT_STOP_CFM, 0.8, 4);
generic_constraint->setParam(BT_CONSTRAINT_STOP_CFM, 0.8, 5);

and the positioning and all. Could that be an activation state issue? It seems the constraint force is only active when the constraint moves and becomes inactive when it doesn't. But I don't quite understand what would be a starting point.

Thanks for any input,

Re: strength of grabbing 6dof Constraint

Posted: Thu Aug 14, 2014 12:03 pm
by Moose
Digging deeper revealed the problem on our side. :roll:
My bad. Some unknown to me method disabled the constraint in those cases...

Please excuse the noise.