393 lines
19 KiB
C++
393 lines
19 KiB
C++
/********************************************************************************
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* ReactPhysics3D physics library, http://www.reactphysics3d.com *
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* Copyright (c) 2010-2018 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 "FixedJoint.h"
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#include "systems/ConstraintSolverSystem.h"
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#include "components/RigidBodyComponents.h"
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#include "engine/DynamicsWorld.h"
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using namespace reactphysics3d;
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// Static variables definition
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const decimal FixedJoint::BETA = decimal(0.2);
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// Constructor
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FixedJoint::FixedJoint(Entity entity, DynamicsWorld &world, const FixedJointInfo& jointInfo)
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: Joint(entity, world, jointInfo), mImpulseTranslation(0, 0, 0), mImpulseRotation(0, 0, 0) {
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// Compute the local-space anchor point for each body
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const Transform& transform1 = mWorld.mTransformComponents.getTransform(jointInfo.body1->getEntity());
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const Transform& transform2 = mWorld.mTransformComponents.getTransform(jointInfo.body2->getEntity());
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mLocalAnchorPointBody1 = transform1.getInverse() * jointInfo.anchorPointWorldSpace;
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mLocalAnchorPointBody2 = transform2.getInverse() * jointInfo.anchorPointWorldSpace;
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// Store inverse of initial rotation from body 1 to body 2 in body 1 space:
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//
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// q20 = q10 r0
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// <=> r0 = q10^-1 q20
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// <=> r0^-1 = q20^-1 q10
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//
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// where:
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//
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// q20 = initial orientation of body 2
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// q10 = initial orientation of body 1
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// r0 = initial rotation rotation from body 1 to body 2
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mInitOrientationDifferenceInv = transform2.getOrientation().getInverse() * transform1.getOrientation();
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}
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// Initialize before solving the constraint
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void FixedJoint::initBeforeSolve(const ConstraintSolverData& constraintSolverData) {
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// Get the bodies entities
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Entity body1Entity = mWorld.mJointsComponents.getBody1Entity(mEntity);
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Entity body2Entity = mWorld.mJointsComponents.getBody2Entity(mEntity);
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// TODO : Remove this and use compoents instead of pointers to bodies
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RigidBody* body1 = static_cast<RigidBody*>(mWorld.mRigidBodyComponents.getRigidBody(body1Entity));
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RigidBody* body2 = static_cast<RigidBody*>(mWorld.mRigidBodyComponents.getRigidBody(body2Entity));
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// Get the bodies positions and orientations
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const Vector3& x1 = constraintSolverData.rigidBodyComponents.getCenterOfMassWorld(body1Entity);
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const Vector3& x2 = constraintSolverData.rigidBodyComponents.getCenterOfMassWorld(body2Entity);
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const Quaternion& orientationBody1 = body1->getTransform().getOrientation();
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const Quaternion& orientationBody2 = body2->getTransform().getOrientation();
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// Get the inertia tensor of bodies
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mI1 = body1->getInertiaTensorInverseWorld();
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mI2 = body2->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) for the 3 translation constraints
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const decimal body1MassInverse = constraintSolverData.rigidBodyComponents.getMassInverse(body1->getEntity());
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const decimal body2MassInverse = constraintSolverData.rigidBodyComponents.getMassInverse(body2->getEntity());
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const decimal inverseMassBodies = body1MassInverse + body2MassInverse;
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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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skewSymmetricMatrixU1 * mI1 * skewSymmetricMatrixU1.getTranspose() +
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skewSymmetricMatrixU2 * mI2 * skewSymmetricMatrixU2.getTranspose();
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// Compute the inverse mass matrix K^-1 for the 3 translation constraints
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mInverseMassMatrixTranslation.setToZero();
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if (mWorld.mRigidBodyComponents.getBodyType(body1Entity) == BodyType::DYNAMIC ||
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mWorld.mRigidBodyComponents.getBodyType(body2Entity) == BodyType::DYNAMIC) {
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mInverseMassMatrixTranslation = massMatrix.getInverse();
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}
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// Compute the bias "b" of the constraint for the 3 translation constraints
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decimal biasFactor = (BETA / constraintSolverData.timeStep);
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mBiasTranslation.setToZero();
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if (mWorld.mJointsComponents.getPositionCorrectionTechnique(mEntity) == JointsPositionCorrectionTechnique::BAUMGARTE_JOINTS) {
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mBiasTranslation = biasFactor * (x2 + mR2World - x1 - mR1World);
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}
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// Compute the inverse of the mass matrix K=JM^-1J^t for the 3 rotation
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// contraints (3x3 matrix)
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mInverseMassMatrixRotation = mI1 + mI2;
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if (mWorld.mRigidBodyComponents.getBodyType(body1Entity) == BodyType::DYNAMIC ||
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mWorld.mRigidBodyComponents.getBodyType(body2Entity) == BodyType::DYNAMIC) {
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mInverseMassMatrixRotation = mInverseMassMatrixRotation.getInverse();
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}
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// Compute the bias "b" for the 3 rotation constraints
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mBiasRotation.setToZero();
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if (mWorld.mJointsComponents.getPositionCorrectionTechnique(mEntity) == JointsPositionCorrectionTechnique::BAUMGARTE_JOINTS) {
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const Quaternion qError = orientationBody2 * mInitOrientationDifferenceInv * orientationBody1.getInverse();
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mBiasRotation = biasFactor * decimal(2.0) * qError.getVectorV();
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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 impulses
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mImpulseTranslation.setToZero();
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mImpulseRotation.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 FixedJoint::warmstart(const ConstraintSolverData& constraintSolverData) {
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// Get the bodies entities
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Entity body1Entity = mWorld.mJointsComponents.getBody1Entity(mEntity);
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Entity body2Entity = mWorld.mJointsComponents.getBody2Entity(mEntity);
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uint32 dynamicsComponentIndexBody1 = constraintSolverData.rigidBodyComponents.getEntityIndex(body1Entity);
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uint32 dynamicsComponentIndexBody2 = constraintSolverData.rigidBodyComponents.getEntityIndex(body2Entity);
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// Get the velocities
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Vector3& v1 = constraintSolverData.rigidBodyComponents.mConstrainedLinearVelocities[dynamicsComponentIndexBody1];
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Vector3& v2 = constraintSolverData.rigidBodyComponents.mConstrainedLinearVelocities[dynamicsComponentIndexBody2];
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Vector3& w1 = constraintSolverData.rigidBodyComponents.mConstrainedAngularVelocities[dynamicsComponentIndexBody1];
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Vector3& w2 = constraintSolverData.rigidBodyComponents.mConstrainedAngularVelocities[dynamicsComponentIndexBody2];
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// Get the inverse mass of the bodies
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const decimal inverseMassBody1 = constraintSolverData.rigidBodyComponents.getMassInverse(body1Entity);
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const decimal inverseMassBody2 = constraintSolverData.rigidBodyComponents.getMassInverse(body2Entity);
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// Compute the impulse P=J^T * lambda for the 3 translation constraints for body 1
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Vector3 linearImpulseBody1 = -mImpulseTranslation;
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Vector3 angularImpulseBody1 = mImpulseTranslation.cross(mR1World);
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// Compute the impulse P=J^T * lambda for the 3 rotation constraints for body 1
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angularImpulseBody1 += -mImpulseRotation;
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// Apply the impulse to the body 1
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v1 += inverseMassBody1 * linearImpulseBody1;
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w1 += mI1 * angularImpulseBody1;
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// Compute the impulse P=J^T * lambda for the 3 translation constraints for body 2
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Vector3 angularImpulseBody2 = -mImpulseTranslation.cross(mR2World);
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// Compute the impulse P=J^T * lambda for the 3 rotation constraints for body 2
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angularImpulseBody2 += mImpulseRotation;
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// Apply the impulse to the body 2
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v2 += inverseMassBody2 * mImpulseTranslation;
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w2 += mI2 * angularImpulseBody2;
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}
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// Solve the velocity constraint
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void FixedJoint::solveVelocityConstraint(const ConstraintSolverData& constraintSolverData) {
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// Get the bodies entities
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Entity body1Entity = mWorld.mJointsComponents.getBody1Entity(mEntity);
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Entity body2Entity = mWorld.mJointsComponents.getBody2Entity(mEntity);
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uint32 dynamicsComponentIndexBody1 = constraintSolverData.rigidBodyComponents.getEntityIndex(body1Entity);
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uint32 dynamicsComponentIndexBody2 = constraintSolverData.rigidBodyComponents.getEntityIndex(body2Entity);
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// Get the velocities
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Vector3& v1 = constraintSolverData.rigidBodyComponents.mConstrainedLinearVelocities[dynamicsComponentIndexBody1];
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Vector3& v2 = constraintSolverData.rigidBodyComponents.mConstrainedLinearVelocities[dynamicsComponentIndexBody2];
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Vector3& w1 = constraintSolverData.rigidBodyComponents.mConstrainedAngularVelocities[dynamicsComponentIndexBody1];
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Vector3& w2 = constraintSolverData.rigidBodyComponents.mConstrainedAngularVelocities[dynamicsComponentIndexBody2];
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// Get the inverse mass of the bodies
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decimal inverseMassBody1 = constraintSolverData.rigidBodyComponents.getMassInverse(body1Entity);
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decimal inverseMassBody2 = constraintSolverData.rigidBodyComponents.getMassInverse(body2Entity);
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// --------------- Translation Constraints --------------- //
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// Compute J*v for the 3 translation constraints
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const Vector3 JvTranslation = v2 + w2.cross(mR2World) - v1 - w1.cross(mR1World);
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// Compute the Lagrange multiplier lambda
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const Vector3 deltaLambda = mInverseMassMatrixTranslation *
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(-JvTranslation - mBiasTranslation);
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mImpulseTranslation += deltaLambda;
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// Compute the impulse P=J^T * lambda for body 1
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const Vector3 linearImpulseBody1 = -deltaLambda;
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Vector3 angularImpulseBody1 = deltaLambda.cross(mR1World);
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// Apply the impulse to the body 1
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v1 += inverseMassBody1 * linearImpulseBody1;
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w1 += mI1 * angularImpulseBody1;
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// Compute the impulse P=J^T * lambda for body 2
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const Vector3 angularImpulseBody2 = -deltaLambda.cross(mR2World);
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// Apply the impulse to the body 2
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v2 += inverseMassBody2 * deltaLambda;
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w2 += mI2 * angularImpulseBody2;
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// --------------- Rotation Constraints --------------- //
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// Compute J*v for the 3 rotation constraints
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const Vector3 JvRotation = w2 - w1;
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// Compute the Lagrange multiplier lambda for the 3 rotation constraints
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Vector3 deltaLambda2 = mInverseMassMatrixRotation * (-JvRotation - mBiasRotation);
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mImpulseRotation += deltaLambda2;
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// Compute the impulse P=J^T * lambda for the 3 rotation constraints for body 1
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angularImpulseBody1 = -deltaLambda2;
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// Apply the impulse to the body 1
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w1 += mI1 * angularImpulseBody1;
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// Apply the impulse to the body 2
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w2 += mI2 * deltaLambda2;
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}
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// Solve the position constraint (for position error correction)
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void FixedJoint::solvePositionConstraint(const ConstraintSolverData& constraintSolverData) {
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// Get the bodies entities
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Entity body1Entity = mWorld.mJointsComponents.getBody1Entity(mEntity);
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Entity body2Entity = mWorld.mJointsComponents.getBody2Entity(mEntity);
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// TODO : Remove this and use compoents instead of pointers to bodies
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RigidBody* body1 = static_cast<RigidBody*>(mWorld.mRigidBodyComponents.getRigidBody(body1Entity));
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RigidBody* body2 = static_cast<RigidBody*>(mWorld.mRigidBodyComponents.getRigidBody(body2Entity));
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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 (mWorld.mJointsComponents.getPositionCorrectionTechnique(mEntity) != JointsPositionCorrectionTechnique::NON_LINEAR_GAUSS_SEIDEL) return;
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// Get the bodies positions and orientations
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Vector3 x1 = constraintSolverData.rigidBodyComponents.getConstrainedPosition(body1Entity);
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Vector3 x2 = constraintSolverData.rigidBodyComponents.getConstrainedPosition(body2Entity);
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Quaternion q1 = constraintSolverData.rigidBodyComponents.getConstrainedOrientation(body1Entity);
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Quaternion q2 = constraintSolverData.rigidBodyComponents.getConstrainedOrientation(body2Entity);
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// Get the inverse mass and inverse inertia tensors of the bodies
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decimal inverseMassBody1 = constraintSolverData.rigidBodyComponents.getMassInverse(body1Entity);
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decimal inverseMassBody2 = constraintSolverData.rigidBodyComponents.getMassInverse(body2Entity);
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// Recompute the inverse inertia tensors
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mI1 = body1->getInertiaTensorInverseWorld();
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mI2 = body2->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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// --------------- Translation Constraints --------------- //
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// Compute the matrix K=JM^-1J^t (3x3 matrix) for the 3 translation constraints
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decimal inverseMassBodies = inverseMassBody1 + inverseMassBody2;
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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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skewSymmetricMatrixU1 * mI1 * skewSymmetricMatrixU1.getTranspose() +
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skewSymmetricMatrixU2 * mI2 * skewSymmetricMatrixU2.getTranspose();
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mInverseMassMatrixTranslation.setToZero();
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if (mWorld.mRigidBodyComponents.getBodyType(body1Entity) == BodyType::DYNAMIC ||
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mWorld.mRigidBodyComponents.getBodyType(body2Entity) == BodyType::DYNAMIC) {
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mInverseMassMatrixTranslation = massMatrix.getInverse();
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}
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// Compute position error for the 3 translation constraints
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const Vector3 errorTranslation = x2 + mR2World - x1 - mR1World;
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// Compute the Lagrange multiplier lambda
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const Vector3 lambdaTranslation = mInverseMassMatrixTranslation * (-errorTranslation);
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// Compute the impulse of body 1
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Vector3 linearImpulseBody1 = -lambdaTranslation;
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Vector3 angularImpulseBody1 = lambdaTranslation.cross(mR1World);
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// Compute the pseudo velocity of body 1
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const Vector3 v1 = inverseMassBody1 * linearImpulseBody1;
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Vector3 w1 = mI1 * angularImpulseBody1;
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// Update the body position/orientation of body 1
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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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// Compute the impulse of body 2
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Vector3 angularImpulseBody2 = -lambdaTranslation.cross(mR2World);
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// Compute the pseudo velocity of body 2
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const Vector3 v2 = inverseMassBody2 * lambdaTranslation;
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Vector3 w2 = mI2 * angularImpulseBody2;
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// Update the body position/orientation of body 2
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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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// --------------- Rotation Constraints --------------- //
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// Compute the inverse of the mass matrix K=JM^-1J^t for the 3 rotation
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// contraints (3x3 matrix)
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mInverseMassMatrixRotation = mI1 + mI2;
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if (mWorld.mRigidBodyComponents.getBodyType(body1Entity) == BodyType::DYNAMIC ||
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mWorld.mRigidBodyComponents.getBodyType(body2Entity) == BodyType::DYNAMIC) {
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mInverseMassMatrixRotation = mInverseMassMatrixRotation.getInverse();
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}
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// Calculate difference in rotation
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//
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// The rotation should be:
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//
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// q2 = q1 r0
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//
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// But because of drift the actual rotation is:
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//
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// q2 = qError q1 r0
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// <=> qError = q2 r0^-1 q1^-1
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//
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// Where:
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// q1 = current rotation of body 1
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// q2 = current rotation of body 2
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// qError = error that needs to be reduced to zero
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Quaternion qError = q2 * mInitOrientationDifferenceInv * q1.getInverse();
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// A quaternion can be seen as:
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//
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// q = [sin(theta / 2) * v, cos(theta/2)]
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//
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// Where:
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// v = rotation vector
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// theta = rotation angle
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//
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// If we assume theta is small (error is small) then sin(x) = x so an approximation of the error angles is:
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const Vector3 errorRotation = decimal(2.0) * qError.getVectorV();
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// Compute the Lagrange multiplier lambda for the 3 rotation constraints
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Vector3 lambdaRotation = mInverseMassMatrixRotation * (-errorRotation);
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// Compute the impulse P=J^T * lambda for the 3 rotation constraints of body 1
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angularImpulseBody1 = -lambdaRotation;
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// Compute the pseudo velocity of body 1
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w1 = mI1 * angularImpulseBody1;
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// Update the body position/orientation of body 1
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q1 += Quaternion(0, w1) * q1 * decimal(0.5);
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q1.normalize();
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// Compute the pseudo velocity of body 2
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w2 = mI2 * lambdaRotation;
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// Update the body position/orientation of body 2
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q2 += Quaternion(0, w2) * q2 * decimal(0.5);
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q2.normalize();
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constraintSolverData.rigidBodyComponents.setConstrainedPosition(body1Entity, x1);
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constraintSolverData.rigidBodyComponents.setConstrainedPosition(body2Entity, x2);
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constraintSolverData.rigidBodyComponents.setConstrainedOrientation(body1Entity, q1);
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constraintSolverData.rigidBodyComponents.setConstrainedOrientation(body2Entity, q2);
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}
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