why the boxs rotates ?

[sjinny]

i add a box and let it fall on to the ground(plane) and after the box touched the ground it began to rotate unusually and never stop. the bullet demos are don't like this.
why ?

thanks~~

[Erwin Coumans]

How big is the box you add?

Can you compare your setup carefully with a Bullet demo and report differences?

Thanks,
Erwin

[sjinny]

the box shape is

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new btBoxShape( btVector3( 2.5, 2.5, 2.5 ) )

with the mass of 1.0
it falls off from height 10.0 and the ground is at ( 0, 0, 0 )


the bullet initing codes:

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int ModuleBullet::init(void)
{
    btCollisionDispatcher* dispatcher= new btCollisionDispatcher();
	btVector3 worldAabbMin( _worldSize[0][0], _worldSize[0][1], _worldSize[0][2] );
	btVector3 worldAabbMax( _worldSize[1][0], _worldSize[1][1], _worldSize[1][2] );
	btOverlappingPairCache* broadphase= new btAxisSweep3( worldAabbMin, worldAabbMax, _maxProxies );
    btSequentialImpulseConstraintSolver* solver= new btSequentialImpulseConstraintSolver();
    _world= new btDiscreteDynamicsWorld( dispatcher, broadphase, solver );

    _world->setGravity( btVector3( 0, -9.8, 0 ) );
    _timer.getTimeNow( _last_step );

    return 0;
}

i derived the class SceneObject from btDefaultMotionState

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SceneObject::SceneObject( btScalar __mass, btCollisionShape* __shape, const btTransform& __startTrans, const btTransform& __centerOfMassOffset, btScalar __friction, btScalar __restitution, btScalar __linearDamping, btScalar __angularDamping, bool __addToWorld )
: btDefaultMotionState( __startTrans, __centerOfMassOffset )
{
    _body= NULL;
    _inWorld= false;

    btVector3 localInertia( 0, 0, 0 );
    if( __mass != 0.0 ){
        __shape->calculateLocalInertia( __mass, localInertia );
    }
    _body= new btRigidBody( __mass, this, __shape, localInertia, __linearDamping, __angularDamping, __friction, __restitution );

    if( __addToWorld ){
        _bullet->getWorld().addRigidBody( _body );
    }
}

in another class RenderableSceneObject i use the setWorldTransform() to synchronize the Ogre SceneNode with the Bullet rigid body:

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void RenderableSceneObject::setWorldTransform( const btTransform& __centerOfMassWorldTrans )
{
    btDefaultMotionState::setWorldTransform( __centerOfMassWorldTrans );

    const btVector3& p= m_graphicsWorldTrans.getOrigin();
    _node->setPosition( p.x(), p.y(), p.z() );
    btQuaternion& q= m_graphicsWorldTrans.getRotation();
    //q.normalize();
    _node->rotate( Ogre::Quaternion( q.w(), q.x(), q.y(), q.z() ), Node::TS_WORLD );
}

i can't find any differences with the demos.
are there any problems in my codes ?

thanks~~

[sjinny]

i've solved my problem.
in the synchronization of the Ogre::SceneNode and the btRigidBody i use Ogre::SceneNode::rotate() with the btQuaternion as the parameter so the rotation will faster and faster.
i changed it to Ogre::SceneNode::setOrientation() then evrything is fine...