Custom Joints

[mauro78]

Hi!

I've Correctly implemented a Custom Kinematic Joint and LocalSubmitConstraints look like this:

Code: Select all

NewtonUserJointAddLinearRow (mpJoint, &matrix0.m_posit[0], &mPosition[0], &pin0[0]);
   NewtonUserJointAddLinearRow (mpJoint, &matrix0.m_posit[0], &mPosition[0], &pin1[0]);
   NewtonUserJointAddLinearRow (mpJoint, &matrix0.m_posit[0], &mPosition[0], &pin2[0]);

Now I'd like to to limit rotation: I don't want any kind of rotation, Is that possible?
I added for example a limit on Y axis with AddAngularRow...but the object still rotates

Regards

p.s.
I've successfully used CustomKinematicJoint of Newton 2.0 to obtain a similar effect but I'd like to learn how to use Custom Joints so I'm tring to do that

Mauro
http://www.breakinglass.com

[Julio Jerez]

you can check how I do it in the Player controller joints, and you can just cut and past the fragment of code into yuo r own joint.

See the Wiki player controler demo in tutorials 200's

[mauro78]

Hi Julio in the tutorial 202 I don't think that I can see the code....couse You just call subroutine from a library; I found this method in the source code file CustomPlayerController.cpp:

Code: Select all

void CustomPlayerController::SubmitConstraints (dFloat timestep, int threadIndex)
{
   dFloat mag;
   dFloat angle;
   dFloat invIxx;
   dFloat invIyy;
   dFloat invIzz;
   dFloat invMass;
   dMatrix matrix0;
   dMatrix matrix1;
   dVector velocity;

   // save the gravity before collision force are applied
   NewtonBodyGetForceAcc (m_body0, &m_gravity[0]);
   NewtonBodyGetInvMass(m_body0, &invMass, &invIxx, &invIyy, &invIzz);
   m_gravity = m_gravity.Scale (invMass);


   // calculate the position of the pivot point and the Jacobian direction vectors, in global space.
   CalculateGlobalMatrix (m_localMatrix0, m_localMatrix1, matrix0, matrix1);

   // if the body ha rotated by some amount, the there will be a plane of rotation
   dVector lateralDir (matrix0.m_front * matrix1.m_front);
   mag = lateralDir % lateralDir;
   if (mag > 1.0e-6f) {
      // if the side vector is not zero, it means the body has rotated
      mag = dSqrt (mag);
      lateralDir = lateralDir.Scale (1.0f / mag);
      angle = dAsin (mag);

      // add an angular constraint to correct the error angle
      NewtonUserJointAddAngularRow (m_joint, angle, &lateralDir[0]);

      // in theory only one correction is needed, but this produces instability as the body may move sideway.
      // a lateral correction prevent this from happening.
      dVector frontDir (lateralDir * matrix1.m_front);
      NewtonUserJointAddAngularRow (m_joint, 0.0f, &frontDir[0]);
   } else {
      // if the angle error is very small then two angular correction along the plane axis do the trick
      NewtonUserJointAddAngularRow (m_joint, 0.0f, &matrix0.m_up[0]);
      NewtonUserJointAddAngularRow (m_joint, 0.0f, &matrix0.m_right[0]);
   }



   // get linear velocity
   if (m_playerState == m_onLand) {
//      dFloat mag2;
      NewtonBodyGetVelocity(m_body0, &velocity[0]);

      // Get the global matrices of each rigid body.
      const dVector& frontDir = matrix0.m_up;
      const dVector& strafeDir = matrix0.m_right;
      const dVector& upDir = matrix0.m_front;
      dVector desiredVeloc (frontDir.Scale (m_forwardSpeed) + upDir.Scale (velocity % upDir) + strafeDir.Scale (-m_sideSpeed));
   //   dFloat maxSpeed = dAbs (m_forwardSpeed) > dAbs (m_sideSpeed) ? dAbs (m_forwardSpeed) : dAbs (m_sideSpeed);   
   //   mag2 = desiredVeloc % desiredVeloc;
   //   if (mag2 > 1.0e-6f) {
   //      desiredVeloc = desiredVeloc.Scale (maxSpeed /dSqrt (mag2));
   //   }

      NewtonBodySetVelocity(m_body0, &desiredVeloc[0]);
   }
}

so...you're talking about that piece of code??

Regards

Mauro

http://www.breakinglass.com

[Julio Jerez]

yes tha code if you are planning on player controller with some free dof

if you are looking for a fully kynematic joint to controll bodies as if they were kynematic pieces
checkout tutorial 103, It has wiki commnet and the joint has the code. See section with comments

// adding two Kinematic controlled object

It explain how to make them.