282 lines
12 KiB
C++
282 lines
12 KiB
C++
/********************************************************************************
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* ReactPhysics3D physics library, http://code.google.com/p/reactphysics3d/ *
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* Copyright (c) 2010-2013 Daniel Chappuis *
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*********************************************************************************
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* *
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* This software is provided 'as-is', without any express or implied warranty. *
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* In no event will the authors be held liable for any damages arising from the *
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* use of this software. *
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* *
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* Permission is granted to anyone to use this software for any purpose, *
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* including commercial applications, and to alter it and redistribute it *
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* freely, subject to the following restrictions: *
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* *
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* 1. The origin of this software must not be misrepresented; you must not claim *
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* that you wrote the original software. If you use this software in a *
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* product, an acknowledgment in the product documentation would be *
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* appreciated but is not required. *
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* *
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* 2. Altered source versions must be plainly marked as such, and must not be *
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* misrepresented as being the original software. *
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* *
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* 3. This notice may not be removed or altered from any source distribution. *
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* *
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********************************************************************************/
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// Libraries
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#include "BallAndSocketJoint.h"
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#include "../engine/ConstraintSolver.h"
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using namespace reactphysics3d;
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// Static variables definition
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const decimal BallAndSocketJoint::BETA = decimal(0.2);
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// Constructor
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BallAndSocketJoint::BallAndSocketJoint(const BallAndSocketJointInfo& jointInfo)
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: Constraint(jointInfo), mImpulse(Vector3(0, 0, 0)) {
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// Compute the local-space anchor point for each body
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mLocalAnchorPointBody1 = mBody1->getTransform().getInverse() * jointInfo.anchorPointWorldSpace;
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mLocalAnchorPointBody2 = mBody2->getTransform().getInverse() * jointInfo.anchorPointWorldSpace;
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}
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// Destructor
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BallAndSocketJoint::~BallAndSocketJoint() {
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}
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// Initialize before solving the constraint
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void BallAndSocketJoint::initBeforeSolve(const ConstraintSolverData& constraintSolverData) {
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// Initialize the bodies index in the velocity array
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mIndexBody1 = constraintSolverData.mapBodyToConstrainedVelocityIndex.find(mBody1)->second;
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mIndexBody2 = constraintSolverData.mapBodyToConstrainedVelocityIndex.find(mBody2)->second;
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// Get the bodies positions and orientations
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const Vector3& x1 = mBody1->getTransform().getPosition();
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const Vector3& x2 = mBody2->getTransform().getPosition();
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const Quaternion& orientationBody1 = mBody1->getTransform().getOrientation();
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const Quaternion& orientationBody2 = mBody2->getTransform().getOrientation();
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// Get the inertia tensor of bodies
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mI1 = mBody1->getInertiaTensorInverseWorld();
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mI2 = mBody2->getInertiaTensorInverseWorld();
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// Compute the vector from body center to the anchor point in world-space
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mR1World = orientationBody1 * mLocalAnchorPointBody1;
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mR2World = orientationBody2 * mLocalAnchorPointBody2;
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// Compute the corresponding skew-symmetric matrices
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Matrix3x3 skewSymmetricMatrixU1= Matrix3x3::computeSkewSymmetricMatrixForCrossProduct(mR1World);
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Matrix3x3 skewSymmetricMatrixU2= Matrix3x3::computeSkewSymmetricMatrixForCrossProduct(mR2World);
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// Compute the matrix K=JM^-1J^t (3x3 matrix)
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decimal inverseMassBodies = 0.0;
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if (mBody1->getIsMotionEnabled()) {
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inverseMassBodies += mBody1->getMassInverse();
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}
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if (mBody2->getIsMotionEnabled()) {
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inverseMassBodies += mBody2->getMassInverse();
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}
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Matrix3x3 massMatrix = Matrix3x3(inverseMassBodies, 0, 0,
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0, inverseMassBodies, 0,
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0, 0, inverseMassBodies);
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if (mBody1->getIsMotionEnabled()) {
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massMatrix += skewSymmetricMatrixU1 * mI1 * skewSymmetricMatrixU1.getTranspose();
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}
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if (mBody2->getIsMotionEnabled()) {
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massMatrix += skewSymmetricMatrixU2 * mI2 * skewSymmetricMatrixU2.getTranspose();
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}
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// Compute the inverse mass matrix K^-1
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mInverseMassMatrix.setToZero();
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if (mBody1->getIsMotionEnabled() || mBody2->getIsMotionEnabled()) {
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mInverseMassMatrix = massMatrix.getInverse();
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}
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// Compute the bias "b" of the constraint
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mBiasVector.setToZero();
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if (mPositionCorrectionTechnique == BAUMGARTE_JOINTS) {
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decimal biasFactor = (BETA / constraintSolverData.timeStep);
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mBiasVector = biasFactor * (x2 + mR2World - x1 - mR1World);
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}
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// If warm-starting is not enabled
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if (!constraintSolverData.isWarmStartingActive) {
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// Reset the accumulated impulse
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mImpulse.setToZero();
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}
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}
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// Warm start the constraint (apply the previous impulse at the beginning of the step)
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void BallAndSocketJoint::warmstart(const ConstraintSolverData& constraintSolverData) {
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// Get the velocities
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Vector3& v1 = constraintSolverData.linearVelocities[mIndexBody1];
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Vector3& v2 = constraintSolverData.linearVelocities[mIndexBody2];
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Vector3& w1 = constraintSolverData.angularVelocities[mIndexBody1];
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Vector3& w2 = constraintSolverData.angularVelocities[mIndexBody2];
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// Get the inverse mass of the bodies
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const decimal inverseMassBody1 = mBody1->getMassInverse();
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const decimal inverseMassBody2 = mBody2->getMassInverse();
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if (mBody1->getIsMotionEnabled()) {
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// Compute the impulse P=J^T * lambda
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const Vector3 linearImpulseBody1 = -mImpulse;
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const Vector3 angularImpulseBody1 = mImpulse.cross(mR1World);
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// Apply the impulse to the body
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v1 += inverseMassBody1 * linearImpulseBody1;
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w1 += mI1 * angularImpulseBody1;
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}
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if (mBody2->getIsMotionEnabled()) {
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// Compute the impulse P=J^T * lambda
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const Vector3 linearImpulseBody2 = mImpulse;
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const Vector3 angularImpulseBody2 = -mImpulse.cross(mR2World);
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// Apply the impulse to the body
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v2 += inverseMassBody2 * linearImpulseBody2;
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w2 += mI2 * angularImpulseBody2;
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}
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}
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// Solve the velocity constraint
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void BallAndSocketJoint::solveVelocityConstraint(const ConstraintSolverData& constraintSolverData) {
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// Get the velocities
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Vector3& v1 = constraintSolverData.linearVelocities[mIndexBody1];
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Vector3& v2 = constraintSolverData.linearVelocities[mIndexBody2];
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Vector3& w1 = constraintSolverData.angularVelocities[mIndexBody1];
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Vector3& w2 = constraintSolverData.angularVelocities[mIndexBody2];
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// Get the inverse mass of the bodies
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decimal inverseMassBody1 = mBody1->getMassInverse();
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decimal inverseMassBody2 = mBody2->getMassInverse();
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// Compute J*v
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const Vector3 Jv = v2 + w2.cross(mR2World) - v1 - w1.cross(mR1World);
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// Compute the Lagrange multiplier lambda
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const Vector3 deltaLambda = mInverseMassMatrix * (-Jv - mBiasVector);
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mImpulse += deltaLambda;
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if (mBody1->getIsMotionEnabled()) {
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// Compute the impulse P=J^T * lambda
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const Vector3 linearImpulseBody1 = -deltaLambda;
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const Vector3 angularImpulseBody1 = deltaLambda.cross(mR1World);
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// Apply the impulse to the body
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v1 += inverseMassBody1 * linearImpulseBody1;
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w1 += mI1 * angularImpulseBody1;
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}
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if (mBody2->getIsMotionEnabled()) {
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// Compute the impulse P=J^T * lambda
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const Vector3 linearImpulseBody2 = deltaLambda;
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const Vector3 angularImpulseBody2 = -deltaLambda.cross(mR2World);
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// Apply the impulse to the body
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v2 += inverseMassBody2 * linearImpulseBody2;
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w2 += mI2 * angularImpulseBody2;
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}
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}
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// Solve the position constraint (for position error correction)
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void BallAndSocketJoint::solvePositionConstraint(const ConstraintSolverData& constraintSolverData) {
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// If the error position correction technique is not the non-linear-gauss-seidel, we do
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// do not execute this method
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if (mPositionCorrectionTechnique != NON_LINEAR_GAUSS_SEIDEL) return;
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// Get the bodies positions and orientations
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Vector3& x1 = constraintSolverData.positions[mIndexBody1];
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Vector3& x2 = constraintSolverData.positions[mIndexBody2];
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Quaternion& q1 = constraintSolverData.orientations[mIndexBody1];
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Quaternion& q2 = constraintSolverData.orientations[mIndexBody2];
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// Get the inverse mass and inverse inertia tensors of the bodies
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decimal inverseMassBody1 = mBody1->getMassInverse();
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decimal inverseMassBody2 = mBody2->getMassInverse();
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// Recompute the inverse inertia tensors
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mI1 = mBody1->getInertiaTensorInverseWorld();
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mI2 = mBody2->getInertiaTensorInverseWorld();
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// Compute the vector from body center to the anchor point in world-space
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mR1World = q1 * mLocalAnchorPointBody1;
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mR2World = q2 * mLocalAnchorPointBody2;
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// Compute the corresponding skew-symmetric matrices
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Matrix3x3 skewSymmetricMatrixU1= Matrix3x3::computeSkewSymmetricMatrixForCrossProduct(mR1World);
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Matrix3x3 skewSymmetricMatrixU2= Matrix3x3::computeSkewSymmetricMatrixForCrossProduct(mR2World);
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// Recompute the inverse mass matrix K=J^TM^-1J of of the 3 translation constraints
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decimal inverseMassBodies = 0.0;
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if (mBody1->getIsMotionEnabled()) {
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inverseMassBodies += inverseMassBody1;
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}
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if (mBody2->getIsMotionEnabled()) {
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inverseMassBodies += inverseMassBody2;
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}
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Matrix3x3 massMatrix = Matrix3x3(inverseMassBodies, 0, 0,
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0, inverseMassBodies, 0,
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0, 0, inverseMassBodies);
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if (mBody1->getIsMotionEnabled()) {
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massMatrix += skewSymmetricMatrixU1 * mI1 * skewSymmetricMatrixU1.getTranspose();
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}
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if (mBody2->getIsMotionEnabled()) {
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massMatrix += skewSymmetricMatrixU2 * mI2 * skewSymmetricMatrixU2.getTranspose();
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}
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mInverseMassMatrix.setToZero();
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if (mBody1->getIsMotionEnabled() || mBody2->getIsMotionEnabled()) {
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mInverseMassMatrix = massMatrix.getInverse();
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}
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// Compute the constraint error (value of the C(x) function)
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const Vector3 constraintError = (x2 + mR2World - x1 - mR1World);
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// Compute the Lagrange multiplier lambda
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// TODO : Do not solve the system by computing the inverse each time and multiplying with the
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// right-hand side vector but instead use a method to directly solve the linear system.
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const Vector3 lambda = mInverseMassMatrix * (-constraintError);
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// Apply the impulse to the bodies of the joint (directly update the position/orientation)
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if (mBody1->getIsMotionEnabled()) {
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// Compute the impulse
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const Vector3 linearImpulseBody1 = -lambda;
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const Vector3 angularImpulseBody1 = lambda.cross(mR1World);
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// Compute the pseudo velocity
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const Vector3 v1 = inverseMassBody1 * linearImpulseBody1;
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const Vector3 w1 = mI1 * angularImpulseBody1;
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// Update the body position/orientation
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x1 += v1;
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q1 += Quaternion(0, w1) * q1 * decimal(0.5);
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q1.normalize();
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}
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if (mBody2->getIsMotionEnabled()) {
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// Compute the impulse
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const Vector3 linearImpulseBody2 = lambda;
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const Vector3 angularImpulseBody2 = -lambda.cross(mR2World);
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// Compute the pseudo velocity
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const Vector3 v2 = inverseMassBody2 * linearImpulseBody2;
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const Vector3 w2 = mI2 * angularImpulseBody2;
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// Update the body position/orientation
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x2 += v2;
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q2 += Quaternion(0, w2) * q2 * decimal(0.5);
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q2.normalize();
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}
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}
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