btGeneric6DofConstraint limits problem in 2.63-RC1 (and 2.62).

[pico]

Hi Erwin,

i think the "btGeneric6DofConstraint" has a problem in 2.63-RC1 (and 2.62).

The "btGeneric6DofConstraint" rotational limit definition says "free means upper < lower". This doesn't work currently at least for Y axis when using "setAngularVelocity".

TEST CASE:
Create a "btGeneric6DofConstraint" constraint.
Set linear limits to min=-100,max=100.
Set lower/upper limit for X+Z axis. Set upper/lower limit for Y axis.
When now setting an angular velocity for the Y axis it will explode after ~180 degrees.
NOTE: I set for the X/Z axis the angular velocity i got previously with "getAngularVelocity ()"

Maybe its due to the fix someone contributed lately to make ragdolls working better. Or its simply not allowed to use setAngularVelocity on constraints?

[projectileman]

If you could read the btGeneric6DofConstraint documentation, in the line 191, you might notice that btGeneric6DofConstraint has these ranges in its limits:

[*] X = (-PI,PI), in some cases (-INF,INF) when unrestricted
[*] Y = (-PI/2,PI/2)
[*] Z = (-PI,PI), in some cases (INF,INF) when unrestricted

Y must be limited between -PI/2 <= Y < = -PI/2, due of an Euler Angles problem;the only way for finding the Y angle is using ArcSin()
So you have to change the angle of reference for your motor.

You should read this post:
http://www.bulletphysics.com/Bullet/php ... f=9&t=1480


And please, I want you tell me if velocity motors work fine in btGeneric6DofConstraint, Do they ??
Thanks,

[pico]

If you could read the btGeneric6DofConstraint documentation, in the line 191, you might notice that btGeneric6DofConstraint has these ranges in its limits:

[*] X = (-PI,PI), in some cases (-INF,INF) when unrestricted
[*] Y = (-PI/2,PI/2)
[*] Z = (-PI,PI), in some cases (INF,INF) when unrestricted

Y must be limited between -PI/2 <= Y < = -PI/2, due of an Euler Angles problem;the only way for finding the Y angle is using ArcSin()
So you have to change the angle of reference for your motor.

You should read this post:
http://www.bulletphysics.com/Bullet/php ... f=9&t=1480

Thanks for your comments.

The issue is that the current implementation doesn't allow to have the Y axis 'unlocked' by setting lower>upper. Or is there now a different method to 'unlock' a specific axis?

[projectileman]

In a rotational contraint if you restrict either the X axis or the Z axis, you cannot leave Y axis unrestricted. When this situation happens Y should have a valid value between [-PI/2, PI/2] otherwise you will get a gimbal lock problem.

If you want getting Y unrestricted, you must leave X axis and the Z axis unrestriced too. So if you want a rotational motor you'd better choose another axis, either X or Z.

This problem is common in every 6DOF constraints, even the AGEIA Physx engine has this issue (The AGEIA documentation says that The maximum swing angles may be set between 0 and 180°. )