Real-Time Physics Simulation Forum

Could anyone help this problem? PD controller is used in robotics to track a reference trajectory, and it is defined as torque = kp*(q_d - q) + kd*v q_d is the desired position, q is current position, v is the velocity. kp and kd are parameters. My problem is from my experiences, the "set"...

STTrife wrote:I do not use 2 bodies connected by a constraint,...

Not sure how you construct a hierarchy of rigid bodies without constraints?

I worked with irrlicht and bullet before. I depends if you want a kinematic controller or a rigid body controller. I can only tell you somet things about the rigid body controller cause that is what I use. The reaseon I did not use the CharacterController that comes with bullet, it because the manu...

Hi there, I have a few questions concerning the 6dof motors: When setting the targetVelocity of the btTranslationalLimitMotor to 0 it still slowly sinks to the ground due to gravity. It doesn't matter how high m_maxMotorForce is set, the object will steadily move in direction of gravity. How can th...

I have been struggling with similar problems and the best solution I came along is to calculate the relative rotation between two linked objects. If anyone got a better way, I am more than pleased to know that.

I used google cache to get the html version. hope this helps.

http://group.artek-vfx.com/?/file/downl ... U1M2ViYTU=

As far as I can understand, you want to move in the body's coordinate, rather than world coordinate? I think the best way to do this is to set the transformation in body's coordinate as T_body, and get current transformation of the body as T_current, and pass T_current*T_body into setWorldTransform().

Is there any other force in the dynamics world? How long does this deviation begin to be noticeable? If it takes a long time, maybe issues with numeric stability (not sure...).

If it is correct in the direction of (-1, 0, 1), (-1, 0, -1), (1, 0, -1), I can't see why it doesn't in (10, 0, 5).

if you only need to apply force at the center of mass, then go for the applycentralforce etc. If you choose apply force, you need to specify both the force and the position on which it is applied. Really depends on your situation.

I just wanna double check this: so you are basically setting the high and low limits both to your target angle to control the joint, rather than computing the torques?

Thanks man, you are so helpful!

Hi, zero gravity can be set with: (I didn't use before, but should work) void btRigidBody::setGravity(const btVector3& acceleration) About the fixed y axis problem, you can get the rotation of the object first, and multiply with the force, which essentially transform the force to the object coor...

void btConeTwistConstraint::setMotorTarget(const btQuaternion &q) { btTransform trACur = m_rbA.getCenterOfMassTransform(); btTransform trBCur = m_rbB.getCenterOfMassTransform(); btQuaternion qConstraint = m_rbBFrame.getRotation().inverse() * q * m_rbAFrame.getRotation(); setMotorTargetInConstra...

But if you think, that 64-bit processor can work with 2 32-bit-long words and when you swtich it to 64-bit,and you are expecting it will be 2*slower, that is not correct. Speed of simulation is not affected by 64-bit precision in this way. Hi Lukas, Thanks for the explanation, I did think that 64-b...

Hi Shepherd, What do you mean with "the speed doesn't slow down too much"? Speed of what? What do you expect to see? And what do you really see? The way, I have realized double precision has affect to quality of simulation, that my Hexapod was shaking/jittering after I have reinstalled Bu...

Sorry, I think I found the reason, the libOpenGLSupport.a should be updated as well.

Cheers.