Search found 10 matches

by acx01b
Fri May 22, 2009 10:00 am
Forum: General Bullet Physics Support and Feedback
Topic: simulation of robot Arm
Replies: 2
Views: 1588

Re: simulation of robot Arm

hi

you have 2 possibilities with btHingeConstraint

joint->setLimit(desiredAngle,desiredAngle,0.0, 1.0,0.0);

or

velocity = (desiredAngle - currentAngle)/timeStep;
joint->enableAngularMotor(true,velocity,10000000);

be careful with solverInfo.m_numIteration, solverInfo.m_erp and timeStep
by acx01b
Tue May 19, 2009 12:27 pm
Forum: General Bullet Physics Support and Feedback
Topic: energy spent for joint motor, difficulty 2.73 --> 2.74
Replies: 5
Views: 2280

Re: energy spent for joint motor, difficulty 2.73 --> 2.74

I need it as quality criterion for evolutionary algorithm

yes you are right, I am going to use "the sum of impulse" instead of "the sum of impulse^2"

so my problem is still there : how to get efficiently after each step the sum of [hingeJoint 6th row].appliedImpulse ?

tks
by acx01b
Mon May 18, 2009 11:12 am
Forum: General Bullet Physics Support and Feedback
Topic: energy spent for joint motor, difficulty 2.73 --> 2.74
Replies: 5
Views: 2280

Re: energy spent for joint motor, difficulty 2.73 --> 2.74

yes, I agree with you but here I consider 1/ timeStep^2 as a constant
by acx01b
Mon May 18, 2009 10:05 am
Forum: General Bullet Physics Support and Feedback
Topic: energy spent for joint motor, difficulty 2.73 --> 2.74
Replies: 5
Views: 2280

Re: energy spent for joint motor, difficulty 2.73 --> 2.74

I find what value I had to sum / save to get total energy applied to hinge joints : btScalar btSequentialImpulseConstraintSolver::solveGroupCacheFriendlyIterations(...) { float totalEnergy = 0; for ( iteration = 0;iteration<infoGlobal.m_numIterations;iteration++) { .... ///solve all joint constraint...
by acx01b
Sun May 17, 2009 5:38 pm
Forum: General Bullet Physics Support and Feedback
Topic: energy spent for joint motor, difficulty 2.73 --> 2.74
Replies: 5
Views: 2280

energy spent for joint motor, difficulty 2.73 --> 2.74

Hi, I would like to know how to get the total energy applied by motors to each hinge joint of my simulation, I can get it like that in bullet 2.73 : // before the Step : for (int = 0; i < nb_joint; i++) { joint[i]->motorImpulseInThatStep = 0; } // modification of btHingeConstraint::solveConstraintOb...
by acx01b
Mon May 11, 2009 9:55 am
Forum: General Bullet Physics Support and Feedback
Topic: robot simulation parameter : num_iteration & timeStep
Replies: 3
Views: 1128

Re: robot simulation parameter : num_iteration & timeStep

thank you to have answered, I have : core2 duo T5xxx, windows vista, bullet 2.74, release -O2, collision disabled between linked bodies and the log I get : Profiling: Root (total running time: 1251.426 ms) --- 0 -- internalSingleStepSimulation (0.08 %) :: 1.#IO ms / frame (1 calls) Unaccounted: (99....
by acx01b
Sat May 09, 2009 8:54 am
Forum: General Bullet Physics Support and Feedback
Topic: robot simulation parameter : num_iteration & timeStep
Replies: 3
Views: 1128

robot simulation parameter : num_iteration & timeStep

Hello, I made a very simple simulation of a robot (a dog) with 14 hinge joints, each body is a cube, except the foots that are spheres (for the collision with the floor), the floor is a cube I found that to get joints' error smaller ( < 0.001 radian) I had to set timeStep = 0.001 , and the solver.nu...
by acx01b
Tue Feb 17, 2009 6:35 pm
Forum: General Bullet Physics Support and Feedback
Topic: Forces in a rigid body
Replies: 2
Views: 888

Re: Forces in a rigid body

you could add in btRigidBody.h :

class btRigidBody {
...

btVector3 getTotalForce()
{
return m_totalForce;
}


btVector3 getTotalTorque()
{
return m_totalTorque;
}

}
by acx01b
Tue Feb 17, 2009 6:18 pm
Forum: General Bullet Physics Support and Feedback
Topic: understanding btPoint2PointConstraint and JacobianEntry
Replies: 0
Views: 595

understanding btPoint2PointConstraint and JacobianEntry

Hello, I'm still trying to understand how joints are corrected in Bullet and in physic simulation in general in btJacobianEntry(...) there is a number m_Adiag calculated as follow : with btVector3 currentAxis = (1,0,0), then (0,1,0) and then (0,0,1) btVector3 A_ContactPos = A_jointPosWorld - A_cente...
by acx01b
Fri Feb 13, 2009 4:36 pm
Forum: General Bullet Physics Support and Feedback
Topic: understand constraint : why error is projected onto each axe
Replies: 0
Views: 569

understand constraint : why error is projected onto each axe

hello, I have to understand the calculus used for solving constraints in Bullet, for a student project my first question is : in btPoint2PointConstraint::solveConstraintObsolete (btPoint2PointConstraint is the easier to start with) you find that code : for (int i=0;i<3;i++) { /* blah blah blah */ bt...