Search found 168 matches

by Dr.Shepherd
Thu Jun 27, 2013 11:50 am
Forum: General Bullet Physics Support and Feedback
Topic: Design PD controller with Bullet
Replies: 5
Views: 3348

Design PD controller with Bullet

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" desired p...
by Dr.Shepherd
Mon Jun 03, 2013 2:29 am
Forum: General Bullet Physics Support and Feedback
Topic: [HOW TO] Character Controller (Irrlicht + Bullet)
Replies: 5
Views: 3391

Re: [HOW TO] Character Controller (Irrlicht + Bullet)

STTrife wrote:I do not use 2 bodies connected by a constraint,...
Not sure how you construct a hierarchy of rigid bodies without constraints?
by Dr.Shepherd
Sun Jun 02, 2013 2:33 pm
Forum: General Bullet Physics Support and Feedback
Topic: [HOW TO] Character Controller (Irrlicht + Bullet)
Replies: 5
Views: 3391

Re: [HOW TO] Character Controller (Irrlicht + Bullet)

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...
by Dr.Shepherd
Wed May 08, 2013 6:54 am
Forum: General Bullet Physics Support and Feedback
Topic: 6dof motor targetVelocity/Position?
Replies: 4
Views: 2454

Re: 6dof motor targetVelocity/Position?

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...
by Dr.Shepherd
Tue Apr 30, 2013 8:13 pm
Forum: General Bullet Physics Support and Feedback
Topic: Determine angular velocities in btGeneric6DofConstraint
Replies: 1
Views: 1645

Re: Determine angular velocities in btGeneric6DofConstraint

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.
by Dr.Shepherd
Tue Apr 02, 2013 8:40 pm
Forum: General Bullet Physics Support and Feedback
Topic: [Help] Controlling a spaceship
Replies: 6
Views: 3272

Re: [Help] Controlling a spaceship

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().
by Dr.Shepherd
Fri Mar 29, 2013 10:38 pm
Forum: General Bullet Physics Support and Feedback
Topic: Rolling Friction Issue
Replies: 5
Views: 3577

Re: Rolling Friction Issue

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).
by Dr.Shepherd
Tue Mar 26, 2013 9:10 pm
Forum: General Bullet Physics Support and Feedback
Topic: [Help] Controlling a spaceship
Replies: 6
Views: 3272

Re: [Help] Controlling a spaceship

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.
by Dr.Shepherd
Tue Mar 26, 2013 5:28 pm
Forum: Applications, Games, Demos or Movies using Bullet
Topic: Six legged robot
Replies: 20
Views: 11631

Re: Six legged robot

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!
by Dr.Shepherd
Mon Mar 25, 2013 10:43 pm
Forum: General Bullet Physics Support and Feedback
Topic: [Help] Controlling a spaceship
Replies: 6
Views: 3272

Re: [Help] Controlling a spaceship

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 coordina...
by Dr.Shepherd
Mon Mar 25, 2013 10:36 pm
Forum: General Bullet Physics Support and Feedback
Topic: ConeTwistConstraint SetMotorTarget
Replies: 0
Views: 1188

ConeTwistConstraint SetMotorTarget

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(); setMotorTargetInConstraintS...
by Dr.Shepherd
Mon Mar 25, 2013 5:40 pm
Forum: Applications, Games, Demos or Movies using Bullet
Topic: Six legged robot
Replies: 20
Views: 11631

Re: Six legged robot

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...
by Dr.Shepherd
Sat Mar 23, 2013 9:32 pm
Forum: Applications, Games, Demos or Movies using Bullet
Topic: Six legged robot
Replies: 20
Views: 11631

Re: Six legged robot

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 BulletPhysic...
by Dr.Shepherd
Sat Mar 23, 2013 5:01 pm
Forum: General Bullet Physics Support and Feedback
Topic: Double Precision Problem
Replies: 1
Views: 1227

Re: Double Precision Problem

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

Cheers.