/*
* Java port of Bullet (c) 2008 Martin Dvorak <jezek2@advel.cz>
*
* Bullet Continuous Collision Detection and Physics Library
* Copyright (c) 2003-2008 Erwin Coumans http://www.bulletphysics.com/
*
* This software is provided 'as-is', without any express or implied warranty.
* In no event will the authors be held liable for any damages arising from
* the use of this software.
*
* Permission is granted to anyone to use this software for any purpose,
* including commercial applications, and to alter it and redistribute it
* freely, subject to the following restrictions:
*
* 1. The origin of this software must not be misrepresented; you must not
* claim that you wrote the original software. If you use this software
* in a product, an acknowledgment in the product documentation would be
* appreciated but is not required.
* 2. Altered source versions must be plainly marked as such, and must not be
* misrepresented as being the original software.
* 3. This notice may not be removed or altered from any source distribution.
*/
package com.bulletphysics.dynamics.constraintsolver;
import com.bulletphysics.dynamics.RigidBody;
import com.bulletphysics.linearmath.Transform;
import com.bulletphysics.linearmath.VectorUtil;
import cz.advel.stack.Stack;
import javax.vecmath.Matrix3f;
import javax.vecmath.Vector3f;
/**
* Point to point constraint between two rigid bodies each with a pivot point that
* descibes the "ballsocket" location in local space.
*
* @author jezek2
*/
public class Point2PointConstraint extends TypedConstraint {
private final JacobianEntry[] jac = new JacobianEntry[]/*[3]*/ { new JacobianEntry(), new JacobianEntry(), new JacobianEntry() }; // 3 orthogonal linear constraints
private final Vector3f pivotInA = new Vector3f();
private final Vector3f pivotInB = new Vector3f();
public ConstraintSetting setting = new ConstraintSetting();
public Point2PointConstraint() {
super(TypedConstraintType.POINT2POINT_CONSTRAINT_TYPE);
}
public Point2PointConstraint(RigidBody rbA, RigidBody rbB, Vector3f pivotInA, Vector3f pivotInB) {
super(TypedConstraintType.POINT2POINT_CONSTRAINT_TYPE, rbA, rbB);
this.pivotInA.set(pivotInA);
this.pivotInB.set(pivotInB);
}
public Point2PointConstraint(RigidBody rbA, Vector3f pivotInA) {
super(TypedConstraintType.POINT2POINT_CONSTRAINT_TYPE, rbA);
this.pivotInA.set(pivotInA);
this.pivotInB.set(pivotInA);
rbA.getCenterOfMassTransform(Stack.alloc(Transform.class)).transform(this.pivotInB);
}
@Override
public void buildJacobian() {
appliedImpulse = 0f;
Vector3f normal = Stack.alloc(Vector3f.class);
normal.set(0f, 0f, 0f);
Matrix3f tmpMat1 = Stack.alloc(Matrix3f.class);
Matrix3f tmpMat2 = Stack.alloc(Matrix3f.class);
Vector3f tmp1 = Stack.alloc(Vector3f.class);
Vector3f tmp2 = Stack.alloc(Vector3f.class);
Vector3f tmpVec = Stack.alloc(Vector3f.class);
Transform centerOfMassA = rbA.getCenterOfMassTransform(Stack.alloc(Transform.class));
Transform centerOfMassB = rbB.getCenterOfMassTransform(Stack.alloc(Transform.class));
for (int i = 0; i < 3; i++) {
VectorUtil.setCoord(normal, i, 1f);
tmpMat1.transpose(centerOfMassA.basis);
tmpMat2.transpose(centerOfMassB.basis);
tmp1.set(pivotInA);
centerOfMassA.transform(tmp1);
tmp1.sub(rbA.getCenterOfMassPosition(tmpVec));
tmp2.set(pivotInB);
centerOfMassB.transform(tmp2);
tmp2.sub(rbB.getCenterOfMassPosition(tmpVec));
jac[i].init(
tmpMat1,
tmpMat2,
tmp1,
tmp2,
normal,
rbA.getInvInertiaDiagLocal(Stack.alloc(Vector3f.class)),
rbA.getInvMass(),
rbB.getInvInertiaDiagLocal(Stack.alloc(Vector3f.class)),
rbB.getInvMass());
VectorUtil.setCoord(normal, i, 0f);
}
}
@Override
public void solveConstraint(float timeStep) {
Vector3f tmp = Stack.alloc(Vector3f.class);
Vector3f tmp2 = Stack.alloc(Vector3f.class);
Vector3f tmpVec = Stack.alloc(Vector3f.class);
Transform centerOfMassA = rbA.getCenterOfMassTransform(Stack.alloc(Transform.class));
Transform centerOfMassB = rbB.getCenterOfMassTransform(Stack.alloc(Transform.class));
Vector3f pivotAInW = Stack.alloc(pivotInA);
centerOfMassA.transform(pivotAInW);
Vector3f pivotBInW = Stack.alloc(pivotInB);
centerOfMassB.transform(pivotBInW);
Vector3f normal = Stack.alloc(Vector3f.class);
normal.set(0f, 0f, 0f);
//btVector3 angvelA = m_rbA.getCenterOfMassTransform().getBasis().transpose() * m_rbA.getAngularVelocity();
//btVector3 angvelB = m_rbB.getCenterOfMassTransform().getBasis().transpose() * m_rbB.getAngularVelocity();
for (int i = 0; i < 3; i++) {
VectorUtil.setCoord(normal, i, 1f);
float jacDiagABInv = 1f / jac[i].getDiagonal();
Vector3f rel_pos1 = Stack.alloc(Vector3f.class);
rel_pos1.sub(pivotAInW, rbA.getCenterOfMassPosition(tmpVec));
Vector3f rel_pos2 = Stack.alloc(Vector3f.class);
rel_pos2.sub(pivotBInW, rbB.getCenterOfMassPosition(tmpVec));
// this jacobian entry could be re-used for all iterations
Vector3f vel1 = rbA.getVelocityInLocalPoint(rel_pos1, Stack.alloc(Vector3f.class));
Vector3f vel2 = rbB.getVelocityInLocalPoint(rel_pos2, Stack.alloc(Vector3f.class));
Vector3f vel = Stack.alloc(Vector3f.class);
vel.sub(vel1, vel2);
float rel_vel;
rel_vel = normal.dot(vel);
/*
//velocity error (first order error)
btScalar rel_vel = m_jac[i].getRelativeVelocity(m_rbA.getLinearVelocity(),angvelA,
m_rbB.getLinearVelocity(),angvelB);
*/
// positional error (zeroth order error)
tmp.sub(pivotAInW, pivotBInW);
float depth = -tmp.dot(normal); //this is the error projected on the normal
float impulse = depth * setting.tau / timeStep * jacDiagABInv - setting.damping * rel_vel * jacDiagABInv;
float impulseClamp = setting.impulseClamp;
if (impulseClamp > 0f) {
if (impulse < -impulseClamp) {
impulse = -impulseClamp;
}
if (impulse > impulseClamp) {
impulse = impulseClamp;
}
}
appliedImpulse += impulse;
Vector3f impulse_vector = Stack.alloc(Vector3f.class);
impulse_vector.scale(impulse, normal);
tmp.sub(pivotAInW, rbA.getCenterOfMassPosition(tmpVec));
rbA.applyImpulse(impulse_vector, tmp);
tmp.negate(impulse_vector);
tmp2.sub(pivotBInW, rbB.getCenterOfMassPosition(tmpVec));
rbB.applyImpulse(tmp, tmp2);
VectorUtil.setCoord(normal, i, 0f);
}
}
public void updateRHS(float timeStep) {
}
public void setPivotA(Vector3f pivotA) {
pivotInA.set(pivotA);
}
public void setPivotB(Vector3f pivotB) {
pivotInB.set(pivotB);
}
public Vector3f getPivotInA(Vector3f out) {
out.set(pivotInA);
return out;
}
public Vector3f getPivotInB(Vector3f out) {
out.set(pivotInB);
return out;
}
////////////////////////////////////////////////////////////////////////////
public static class ConstraintSetting {
public float tau = 0.3f;
public float damping = 1f;
public float impulseClamp = 0f;
}
}