Rigid Body Constraint Question

[sio2interactive]

Im trying to put a 2 axis constraint on a rigid body, and Im using btHingeConstraint, this is my initialization code below:

Code: Select all

		const btVector3 pivot( 0.0f, 0.0f, -radius );
		btVector3 axis( 1.0f, 0.0f, 0.0f );
		btHingeConstraint *_btHingeConstraint = new btHingeConstraint( *_btRigidBody, pivot, axis );
		_btSoftRigidDynamicsWorld->addConstraint( _btHingeConstraint, true );

and im using _btRigidBody->setAngularVelocity( btVector3( -180.0f, 0.0f, 0.0f ) ); to test the constraint on the X axis and everything is fine...

The problem comes when I try to put the constraint on the X and Y axis at the same time... to do so I modify the following code:

btVector3 axis( 1.0f, 1.0f, 0.0f );

and use:

_btRigidBody->setAngularVelocity( btVector3( -180.0f, -180.0f, 0.0f ) ); in order to test, but my rigid body is like going offscreen and disappear...

I also try to create 2 separate constraint 1 on X and 1 on Y, and use 2 separate setAngularVelocity call but no success...

What Im am doing wrong? Is there a way to put 2 constraint on different axis on a rigid body? What Im trying to do is like a punching bag ( a cylinder attached to a certain point in space ) that when I click it "angles" on the X and Y axis simultaneously... Help!

Tks in advance,

Cheers,

[Erwin Coumans]

The btHingeConstraint only has a single axis (and this axis should be unit length), so it is not suitable.

For a punching bag, you could consider using one of the following:

• btConeTwistConstraint with limits, see Demos\RagdollDemo
• btGeneric6DofConstraint with limits, see Demos\GenericJointDemo
• btPoint2PointConstraint, and make sure the collision detection deals with limits
• a soft body rope

Hope this helps,
Erwin

[sio2interactive]

Allright got it! It help a bunch tks!