229 lines
7.9 KiB
C++
229 lines
7.9 KiB
C++
/*
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Bullet Continuous Collision Detection and Physics Library
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Copyright (c) 2003-2006 Erwin Coumans http://continuousphysics.com/Bullet/
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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 use of this software.
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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 freely,
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subject to the following restrictions:
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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.
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2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
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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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#include "btHingeConstraint.h"
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#include "BulletDynamics/Dynamics/btRigidBody.h"
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#include "LinearMath/btTransformUtil.h"
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#include <new>
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btHingeConstraint::btHingeConstraint():
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m_enableAngularMotor(false)
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{
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}
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btHingeConstraint::btHingeConstraint(btRigidBody& rbA,btRigidBody& rbB, const btVector3& pivotInA,const btVector3& pivotInB,
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btVector3& axisInA,btVector3& axisInB)
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:btTypedConstraint(rbA,rbB),m_pivotInA(pivotInA),m_pivotInB(pivotInB),
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m_axisInA(axisInA),
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m_axisInB(-axisInB),
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m_angularOnly(false),
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m_enableAngularMotor(false)
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{
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}
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btHingeConstraint::btHingeConstraint(btRigidBody& rbA,const btVector3& pivotInA,btVector3& axisInA)
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:btTypedConstraint(rbA),m_pivotInA(pivotInA),m_pivotInB(rbA.getCenterOfMassTransform()(pivotInA)),
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m_axisInA(axisInA),
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//fixed axis in worldspace
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m_axisInB(rbA.getCenterOfMassTransform().getBasis() * -axisInA),
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m_angularOnly(false),
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m_enableAngularMotor(false)
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{
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}
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void btHingeConstraint::buildJacobian()
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{
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m_appliedImpulse = btScalar(0.);
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btVector3 normal(0,0,0);
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if (!m_angularOnly)
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{
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for (int i=0;i<3;i++)
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{
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normal[i] = 1;
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new (&m_jac[i]) btJacobianEntry(
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m_rbA.getCenterOfMassTransform().getBasis().transpose(),
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m_rbB.getCenterOfMassTransform().getBasis().transpose(),
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m_rbA.getCenterOfMassTransform()*m_pivotInA - m_rbA.getCenterOfMassPosition(),
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m_rbB.getCenterOfMassTransform()*m_pivotInB - m_rbB.getCenterOfMassPosition(),
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normal,
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m_rbA.getInvInertiaDiagLocal(),
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m_rbA.getInvMass(),
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m_rbB.getInvInertiaDiagLocal(),
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m_rbB.getInvMass());
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normal[i] = 0;
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}
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}
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//calculate two perpendicular jointAxis, orthogonal to hingeAxis
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//these two jointAxis require equal angular velocities for both bodies
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//this is unused for now, it's a todo
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btVector3 jointAxis0local;
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btVector3 jointAxis1local;
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btPlaneSpace1(m_axisInA,jointAxis0local,jointAxis1local);
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getRigidBodyA().getCenterOfMassTransform().getBasis() * m_axisInA;
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btVector3 jointAxis0 = getRigidBodyA().getCenterOfMassTransform().getBasis() * jointAxis0local;
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btVector3 jointAxis1 = getRigidBodyA().getCenterOfMassTransform().getBasis() * jointAxis1local;
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btVector3 hingeAxisWorld = getRigidBodyA().getCenterOfMassTransform().getBasis() * m_axisInA;
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new (&m_jacAng[0]) btJacobianEntry(jointAxis0,
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m_rbA.getCenterOfMassTransform().getBasis().transpose(),
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m_rbB.getCenterOfMassTransform().getBasis().transpose(),
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m_rbA.getInvInertiaDiagLocal(),
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m_rbB.getInvInertiaDiagLocal());
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new (&m_jacAng[1]) btJacobianEntry(jointAxis1,
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m_rbA.getCenterOfMassTransform().getBasis().transpose(),
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m_rbB.getCenterOfMassTransform().getBasis().transpose(),
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m_rbA.getInvInertiaDiagLocal(),
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m_rbB.getInvInertiaDiagLocal());
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new (&m_jacAng[2]) btJacobianEntry(hingeAxisWorld,
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m_rbA.getCenterOfMassTransform().getBasis().transpose(),
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m_rbB.getCenterOfMassTransform().getBasis().transpose(),
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m_rbA.getInvInertiaDiagLocal(),
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m_rbB.getInvInertiaDiagLocal());
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}
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void btHingeConstraint::solveConstraint(btScalar timeStep)
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{
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btVector3 pivotAInW = m_rbA.getCenterOfMassTransform()*m_pivotInA;
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btVector3 pivotBInW = m_rbB.getCenterOfMassTransform()*m_pivotInB;
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btVector3 normal(0,0,0);
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btScalar tau = btScalar(0.3);
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btScalar damping = btScalar(1.);
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//linear part
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if (!m_angularOnly)
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{
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for (int i=0;i<3;i++)
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{
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normal[i] = 1;
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btScalar jacDiagABInv = btScalar(1.) / m_jac[i].getDiagonal();
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btVector3 rel_pos1 = pivotAInW - m_rbA.getCenterOfMassPosition();
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btVector3 rel_pos2 = pivotBInW - m_rbB.getCenterOfMassPosition();
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btVector3 vel1 = m_rbA.getVelocityInLocalPoint(rel_pos1);
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btVector3 vel2 = m_rbB.getVelocityInLocalPoint(rel_pos2);
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btVector3 vel = vel1 - vel2;
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btScalar rel_vel;
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rel_vel = normal.dot(vel);
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//positional error (zeroth order error)
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btScalar depth = -(pivotAInW - pivotBInW).dot(normal); //this is the error projected on the normal
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btScalar impulse = depth*tau/timeStep * jacDiagABInv - damping * rel_vel * jacDiagABInv * damping;
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m_appliedImpulse += impulse;
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btVector3 impulse_vector = normal * impulse;
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m_rbA.applyImpulse(impulse_vector, pivotAInW - m_rbA.getCenterOfMassPosition());
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m_rbB.applyImpulse(-impulse_vector, pivotBInW - m_rbB.getCenterOfMassPosition());
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normal[i] = 0;
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}
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}
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{
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///solve angular part
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// get axes in world space
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btVector3 axisA = getRigidBodyA().getCenterOfMassTransform().getBasis() * m_axisInA;
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btVector3 axisB = getRigidBodyB().getCenterOfMassTransform().getBasis() * m_axisInB;
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const btVector3& angVelA = getRigidBodyA().getAngularVelocity();
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const btVector3& angVelB = getRigidBodyB().getAngularVelocity();
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btVector3 angVelAroundHingeAxisA = axisA * axisA.dot(angVelA);
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btVector3 angVelAroundHingeAxisB = axisB * axisB.dot(angVelB);
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btVector3 angAorthog = angVelA - angVelAroundHingeAxisA;
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btVector3 angBorthog = angVelB - angVelAroundHingeAxisB;
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btVector3 velrelOrthog = angAorthog-angBorthog;
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{
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//solve orthogonal angular velocity correction
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btScalar relaxation = btScalar(1.);
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btScalar len = velrelOrthog.length();
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if (len > btScalar(0.00001))
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{
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btVector3 normal = velrelOrthog.normalized();
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btScalar denom = getRigidBodyA().computeAngularImpulseDenominator(normal) +
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getRigidBodyB().computeAngularImpulseDenominator(normal);
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// scale for mass and relaxation
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//todo: expose this 0.9 factor to developer
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velrelOrthog *= (btScalar(1.)/denom) * btScalar(0.9);
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}
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//solve angular positional correction
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btVector3 angularError = -axisA.cross(axisB) *(btScalar(1.)/timeStep);
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btScalar len2 = angularError.length();
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if (len2>btScalar(0.00001))
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{
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btVector3 normal2 = angularError.normalized();
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btScalar denom2 = getRigidBodyA().computeAngularImpulseDenominator(normal2) +
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getRigidBodyB().computeAngularImpulseDenominator(normal2);
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angularError *= (btScalar(1.)/denom2) * relaxation;
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}
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m_rbA.applyTorqueImpulse(-velrelOrthog+angularError);
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m_rbB.applyTorqueImpulse(velrelOrthog-angularError);
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}
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//apply motor
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if (m_enableAngularMotor)
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{
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//todo: add limits too
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btVector3 angularLimit(0,0,0);
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btVector3 velrel = angVelAroundHingeAxisA - angVelAroundHingeAxisB;
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btScalar projRelVel = velrel.dot(axisA);
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btScalar desiredMotorVel = m_motorTargetVelocity;
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btScalar motor_relvel = desiredMotorVel - projRelVel;
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btScalar denom3 = getRigidBodyA().computeAngularImpulseDenominator(axisA) +
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getRigidBodyB().computeAngularImpulseDenominator(axisA);
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btScalar unclippedMotorImpulse = (btScalar(1.)/denom3) * motor_relvel;;
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//todo: should clip against accumulated impulse
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btScalar clippedMotorImpulse = unclippedMotorImpulse > m_maxMotorImpulse ? m_maxMotorImpulse : unclippedMotorImpulse;
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clippedMotorImpulse = clippedMotorImpulse < -m_maxMotorImpulse ? -m_maxMotorImpulse : clippedMotorImpulse;
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btVector3 motorImp = clippedMotorImpulse * axisA;
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m_rbA.applyTorqueImpulse(motorImp+angularLimit);
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m_rbB.applyTorqueImpulse(-motorImp-angularLimit);
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}
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}
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}
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void btHingeConstraint::updateRHS(btScalar timeStep)
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{
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}
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