Can Rigidbodies Turn Around on an Axis of Local Coordinate ?

[zjl19870808]

Hello, everyone. The rigidbodies can turn around on an axis of world coordinate when btRigidBody::applyTorque is called, now the rigidbodies are expected to turn around on an axis of local coordinate, so how can I realize it?
Thank you. Your suggestions will be greatly appreciated
Jet

[zjl19870808]

Hello, everyone. The rigidbodies can turn around on an axis of world coordinate when btRigidBody::applyTorque is called, now the rigidbodies are expected to turn around on an axis of local coordinate, so how can I realize it?
Thank you. Your suggestions will be greatly appreciated
Jet

Anybody know that？I tried to realize it by using multithread, btRigidBody::applyTorque still cannot make the rigidbody turn around on an axis of local coordinate, while btRigidBody::applyCentralForce can move the rigidbody on an axis of local coordinate. My method is as following: I get the angle that the rigidbody rotated, and then make the axis(this is an axis of world coordinate ,such as x axis)which is the parameter of btRigidBody::applyTorque or btRigidBody::applyCentralForce rotate the same angle to reach the same direction as the local coordinate. Here are my codes:

Code: Select all

void ConstraintDemo::driveControl()
{
	btScalar rotatevalue[3];
	btVector3 basicVec;
	while (true)
	{
		basicVec = btVector3(0,0,100);
		rotatevalue[0]=body1->getWorldTransform().getRotation().getX();
		rotatevalue[1]=body1->getWorldTransform().getRotation().getY();
		rotatevalue[2]=body1->getWorldTransform().getRotation().getZ();
		for (int i=0; i<3; i++)
		{
			if (rotatevalue[i]>M_PI && rotatevalue[i]<M_PI*2)
			{
				rotatevalue[i] = M_PI - rotatevalue[i];
			}
			else if (rotatevalue[i]>-2*M_PI && rotatevalue[i]<=-M_PI)
			{
				rotatevalue[i] = M_PI*2 + rotatevalue[i];
			}
			else if (rotatevalue[i] >= 2*M_PI)
			{
				while(!(rotatevalue[i]<M_PI || rotatevalue[i]>-M_PI))
				{
					rotatevalue[i] -= M_PI*2;
				}
			}
			else if (rotatevalue[i] <= -2*M_PI)
			{
				while(!(rotatevalue[i]<M_PI || rotatevalue[i]>-M_PI))
				{
					rotatevalue[i] += 2*M_PI;
				}
			}
			else
			{}
			btAssert((rotatevalue[i]<=M_PI && rotatevalue[i]>=-M_PI));
		}
	
		basicVec = basicVec.rotate(btVector3(1,0,0),(btAsin(rotatevalue[0]))*2);
		basicVec = basicVec.rotate(btVector3(0,1,0),(btAsin(rotatevalue[1]))*2);
		TorqueVec = basicVec.rotate(btVector3(0,0,1),(btAsin(rotatevalue[2]))*2);
	}
}

This is a thread function, and TorqueVec is the parameter of btRigidbody::applyTorque or btRigidbody::applyCentralForce.
Only btRigidbody::applyCentralForce works well. Anybody can give me some suggestions? thank you very much.
Jet

[Erwin Coumans]

If you want to apply a local torque, you need to transform the local torque (or force) into world torque.
This can be done by pre-multiplying by the orientation (or post multiply by its inverse):

Code: Select all

btVector3 worldTorque = body->getWorldTransform().getBasis() * localTorque;
or 
btVector3 worldTorque = localTorque * body->getWorldTransform().getBasis().inverse();

See also http://bulletphysics.org/Bullet/phpBB3/ ... f=9&t=2366
Thanks,
Erwin

[zjl19870808]

If you want to apply a local torque, you need to transform the local torque (or force) into world torque.
This can be done by pre-multiplying by the orientation (or post multiply by its inverse):

Code: Select all

btVector3 worldTorque = body->getWorldTransform().getBasis() * localTorque;
or 
btVector3 worldTorque = localTorque * body->getWorldTransform().getBasis().inverse();

See also http://bulletphysics.org/Bullet/phpBB3/ ... f=9&t=2366
Thanks,
Erwin

Thank you very much! I have solved my problem perfectly.
Jet