420 lines
12 KiB
C++
420 lines
12 KiB
C++
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/*
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* Copyright (c) 2007-2011 Erin Catto http://www.box2d.org
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*
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* This software is provided 'as-is', without any express or implied
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* warranty. In no event will the authors be held liable for any damages
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* 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
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* freely, subject to the following restrictions:
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* 1. The origin of this software must not be misrepresented; you must not
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* claim that you wrote the original software. If you use this software
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* in a product, an acknowledgment in the product documentation would be
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* appreciated but is not required.
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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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* 3. This notice may not be removed or altered from any source distribution.
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*/
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#include "b2GearJoint.h"
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#include "b2RevoluteJoint.h"
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#include "b2PrismaticJoint.h"
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#include "../b2Body.h"
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#include "../b2TimeStep.h"
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// Gear Joint:
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// C0 = (coordinate1 + ratio * coordinate2)_initial
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// C = (coordinate1 + ratio * coordinate2) - C0 = 0
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// J = [J1 ratio * J2]
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// K = J * invM * JT
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// = J1 * invM1 * J1T + ratio * ratio * J2 * invM2 * J2T
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//
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// Revolute:
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// coordinate = rotation
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// Cdot = angularVelocity
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// J = [0 0 1]
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// K = J * invM * JT = invI
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//
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// Prismatic:
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// coordinate = dot(p - pg, ug)
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// Cdot = dot(v + cross(w, r), ug)
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// J = [ug cross(r, ug)]
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// K = J * invM * JT = invMass + invI * cross(r, ug)^2
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b2GearJoint::b2GearJoint(const b2GearJointDef* def)
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: b2Joint(def)
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{
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m_joint1 = def->joint1;
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m_joint2 = def->joint2;
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m_typeA = m_joint1->GetType();
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m_typeB = m_joint2->GetType();
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b2Assert(m_typeA == e_revoluteJoint || m_typeA == e_prismaticJoint);
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b2Assert(m_typeB == e_revoluteJoint || m_typeB == e_prismaticJoint);
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float32 coordinateA, coordinateB;
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// TODO_ERIN there might be some problem with the joint edges in b2Joint.
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m_bodyC = m_joint1->GetBodyA();
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m_bodyA = m_joint1->GetBodyB();
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// Get geometry of joint1
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b2Transform xfA = m_bodyA->m_xf;
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float32 aA = m_bodyA->m_sweep.a;
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b2Transform xfC = m_bodyC->m_xf;
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float32 aC = m_bodyC->m_sweep.a;
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if (m_typeA == e_revoluteJoint)
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{
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b2RevoluteJoint* revolute = (b2RevoluteJoint*)def->joint1;
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m_localAnchorC = revolute->m_localAnchorA;
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m_localAnchorA = revolute->m_localAnchorB;
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m_referenceAngleA = revolute->m_referenceAngle;
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m_localAxisC.SetZero();
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coordinateA = aA - aC - m_referenceAngleA;
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}
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else
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{
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b2PrismaticJoint* prismatic = (b2PrismaticJoint*)def->joint1;
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m_localAnchorC = prismatic->m_localAnchorA;
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m_localAnchorA = prismatic->m_localAnchorB;
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m_referenceAngleA = prismatic->m_referenceAngle;
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m_localAxisC = prismatic->m_localXAxisA;
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b2Vec2 pC = m_localAnchorC;
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b2Vec2 pA = b2MulT(xfC.q, b2Mul(xfA.q, m_localAnchorA) + (xfA.p - xfC.p));
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coordinateA = b2Dot(pA - pC, m_localAxisC);
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}
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m_bodyD = m_joint2->GetBodyA();
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m_bodyB = m_joint2->GetBodyB();
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// Get geometry of joint2
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b2Transform xfB = m_bodyB->m_xf;
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float32 aB = m_bodyB->m_sweep.a;
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b2Transform xfD = m_bodyD->m_xf;
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float32 aD = m_bodyD->m_sweep.a;
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if (m_typeB == e_revoluteJoint)
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{
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b2RevoluteJoint* revolute = (b2RevoluteJoint*)def->joint2;
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m_localAnchorD = revolute->m_localAnchorA;
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m_localAnchorB = revolute->m_localAnchorB;
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m_referenceAngleB = revolute->m_referenceAngle;
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m_localAxisD.SetZero();
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coordinateB = aB - aD - m_referenceAngleB;
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}
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else
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{
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b2PrismaticJoint* prismatic = (b2PrismaticJoint*)def->joint2;
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m_localAnchorD = prismatic->m_localAnchorA;
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m_localAnchorB = prismatic->m_localAnchorB;
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m_referenceAngleB = prismatic->m_referenceAngle;
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m_localAxisD = prismatic->m_localXAxisA;
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b2Vec2 pD = m_localAnchorD;
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b2Vec2 pB = b2MulT(xfD.q, b2Mul(xfB.q, m_localAnchorB) + (xfB.p - xfD.p));
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coordinateB = b2Dot(pB - pD, m_localAxisD);
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}
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m_ratio = def->ratio;
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m_constant = coordinateA + m_ratio * coordinateB;
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m_impulse = 0.0f;
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}
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void b2GearJoint::InitVelocityConstraints(const b2SolverData& data)
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{
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m_indexA = m_bodyA->m_islandIndex;
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m_indexB = m_bodyB->m_islandIndex;
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m_indexC = m_bodyC->m_islandIndex;
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m_indexD = m_bodyD->m_islandIndex;
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m_lcA = m_bodyA->m_sweep.localCenter;
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m_lcB = m_bodyB->m_sweep.localCenter;
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m_lcC = m_bodyC->m_sweep.localCenter;
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m_lcD = m_bodyD->m_sweep.localCenter;
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m_mA = m_bodyA->m_invMass;
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m_mB = m_bodyB->m_invMass;
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m_mC = m_bodyC->m_invMass;
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m_mD = m_bodyD->m_invMass;
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m_iA = m_bodyA->m_invI;
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m_iB = m_bodyB->m_invI;
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m_iC = m_bodyC->m_invI;
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m_iD = m_bodyD->m_invI;
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float32 aA = data.positions[m_indexA].a;
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b2Vec2 vA = data.velocities[m_indexA].v;
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float32 wA = data.velocities[m_indexA].w;
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float32 aB = data.positions[m_indexB].a;
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b2Vec2 vB = data.velocities[m_indexB].v;
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float32 wB = data.velocities[m_indexB].w;
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float32 aC = data.positions[m_indexC].a;
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b2Vec2 vC = data.velocities[m_indexC].v;
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float32 wC = data.velocities[m_indexC].w;
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float32 aD = data.positions[m_indexD].a;
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b2Vec2 vD = data.velocities[m_indexD].v;
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float32 wD = data.velocities[m_indexD].w;
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b2Rot qA(aA), qB(aB), qC(aC), qD(aD);
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m_mass = 0.0f;
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if (m_typeA == e_revoluteJoint)
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{
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m_JvAC.SetZero();
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m_JwA = 1.0f;
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m_JwC = 1.0f;
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m_mass += m_iA + m_iC;
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}
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else
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{
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b2Vec2 u = b2Mul(qC, m_localAxisC);
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b2Vec2 rC = b2Mul(qC, m_localAnchorC - m_lcC);
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b2Vec2 rA = b2Mul(qA, m_localAnchorA - m_lcA);
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m_JvAC = u;
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m_JwC = b2Cross(rC, u);
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m_JwA = b2Cross(rA, u);
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m_mass += m_mC + m_mA + m_iC * m_JwC * m_JwC + m_iA * m_JwA * m_JwA;
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}
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if (m_typeB == e_revoluteJoint)
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{
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m_JvBD.SetZero();
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m_JwB = m_ratio;
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m_JwD = m_ratio;
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m_mass += m_ratio * m_ratio * (m_iB + m_iD);
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}
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else
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{
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b2Vec2 u = b2Mul(qD, m_localAxisD);
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b2Vec2 rD = b2Mul(qD, m_localAnchorD - m_lcD);
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b2Vec2 rB = b2Mul(qB, m_localAnchorB - m_lcB);
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m_JvBD = m_ratio * u;
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m_JwD = m_ratio * b2Cross(rD, u);
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m_JwB = m_ratio * b2Cross(rB, u);
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m_mass += m_ratio * m_ratio * (m_mD + m_mB) + m_iD * m_JwD * m_JwD + m_iB * m_JwB * m_JwB;
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}
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// Compute effective mass.
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m_mass = m_mass > 0.0f ? 1.0f / m_mass : 0.0f;
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if (data.step.warmStarting)
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{
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vA += (m_mA * m_impulse) * m_JvAC;
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wA += m_iA * m_impulse * m_JwA;
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vB += (m_mB * m_impulse) * m_JvBD;
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wB += m_iB * m_impulse * m_JwB;
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vC -= (m_mC * m_impulse) * m_JvAC;
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wC -= m_iC * m_impulse * m_JwC;
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vD -= (m_mD * m_impulse) * m_JvBD;
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wD -= m_iD * m_impulse * m_JwD;
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}
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else
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{
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m_impulse = 0.0f;
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}
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data.velocities[m_indexA].v = vA;
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data.velocities[m_indexA].w = wA;
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data.velocities[m_indexB].v = vB;
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data.velocities[m_indexB].w = wB;
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data.velocities[m_indexC].v = vC;
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data.velocities[m_indexC].w = wC;
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data.velocities[m_indexD].v = vD;
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data.velocities[m_indexD].w = wD;
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}
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void b2GearJoint::SolveVelocityConstraints(const b2SolverData& data)
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{
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b2Vec2 vA = data.velocities[m_indexA].v;
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float32 wA = data.velocities[m_indexA].w;
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b2Vec2 vB = data.velocities[m_indexB].v;
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float32 wB = data.velocities[m_indexB].w;
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b2Vec2 vC = data.velocities[m_indexC].v;
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float32 wC = data.velocities[m_indexC].w;
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b2Vec2 vD = data.velocities[m_indexD].v;
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float32 wD = data.velocities[m_indexD].w;
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float32 Cdot = b2Dot(m_JvAC, vA - vC) + b2Dot(m_JvBD, vB - vD);
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Cdot += (m_JwA * wA - m_JwC * wC) + (m_JwB * wB - m_JwD * wD);
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float32 impulse = -m_mass * Cdot;
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m_impulse += impulse;
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vA += (m_mA * impulse) * m_JvAC;
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wA += m_iA * impulse * m_JwA;
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vB += (m_mB * impulse) * m_JvBD;
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wB += m_iB * impulse * m_JwB;
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vC -= (m_mC * impulse) * m_JvAC;
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wC -= m_iC * impulse * m_JwC;
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vD -= (m_mD * impulse) * m_JvBD;
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wD -= m_iD * impulse * m_JwD;
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data.velocities[m_indexA].v = vA;
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data.velocities[m_indexA].w = wA;
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data.velocities[m_indexB].v = vB;
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data.velocities[m_indexB].w = wB;
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data.velocities[m_indexC].v = vC;
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data.velocities[m_indexC].w = wC;
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data.velocities[m_indexD].v = vD;
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data.velocities[m_indexD].w = wD;
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}
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bool b2GearJoint::SolvePositionConstraints(const b2SolverData& data)
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{
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b2Vec2 cA = data.positions[m_indexA].c;
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float32 aA = data.positions[m_indexA].a;
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b2Vec2 cB = data.positions[m_indexB].c;
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float32 aB = data.positions[m_indexB].a;
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b2Vec2 cC = data.positions[m_indexC].c;
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float32 aC = data.positions[m_indexC].a;
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b2Vec2 cD = data.positions[m_indexD].c;
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float32 aD = data.positions[m_indexD].a;
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b2Rot qA(aA), qB(aB), qC(aC), qD(aD);
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float32 linearError = 0.0f;
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float32 coordinateA, coordinateB;
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b2Vec2 JvAC, JvBD;
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float32 JwA, JwB, JwC, JwD;
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float32 mass = 0.0f;
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if (m_typeA == e_revoluteJoint)
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{
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JvAC.SetZero();
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JwA = 1.0f;
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JwC = 1.0f;
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mass += m_iA + m_iC;
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coordinateA = aA - aC - m_referenceAngleA;
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}
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else
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{
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b2Vec2 u = b2Mul(qC, m_localAxisC);
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b2Vec2 rC = b2Mul(qC, m_localAnchorC - m_lcC);
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b2Vec2 rA = b2Mul(qA, m_localAnchorA - m_lcA);
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JvAC = u;
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JwC = b2Cross(rC, u);
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JwA = b2Cross(rA, u);
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mass += m_mC + m_mA + m_iC * JwC * JwC + m_iA * JwA * JwA;
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b2Vec2 pC = m_localAnchorC - m_lcC;
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b2Vec2 pA = b2MulT(qC, rA + (cA - cC));
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coordinateA = b2Dot(pA - pC, m_localAxisC);
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}
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if (m_typeB == e_revoluteJoint)
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{
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JvBD.SetZero();
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JwB = m_ratio;
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|
JwD = m_ratio;
|
||
|
|
mass += m_ratio * m_ratio * (m_iB + m_iD);
|
||
|
|
|
||
|
|
coordinateB = aB - aD - m_referenceAngleB;
|
||
|
|
}
|
||
|
|
else
|
||
|
|
{
|
||
|
|
b2Vec2 u = b2Mul(qD, m_localAxisD);
|
||
|
|
b2Vec2 rD = b2Mul(qD, m_localAnchorD - m_lcD);
|
||
|
|
b2Vec2 rB = b2Mul(qB, m_localAnchorB - m_lcB);
|
||
|
|
JvBD = m_ratio * u;
|
||
|
|
JwD = m_ratio * b2Cross(rD, u);
|
||
|
|
JwB = m_ratio * b2Cross(rB, u);
|
||
|
|
mass += m_ratio * m_ratio * (m_mD + m_mB) + m_iD * JwD * JwD + m_iB * JwB * JwB;
|
||
|
|
|
||
|
|
b2Vec2 pD = m_localAnchorD - m_lcD;
|
||
|
|
b2Vec2 pB = b2MulT(qD, rB + (cB - cD));
|
||
|
|
coordinateB = b2Dot(pB - pD, m_localAxisD);
|
||
|
|
}
|
||
|
|
|
||
|
|
float32 C = (coordinateA + m_ratio * coordinateB) - m_constant;
|
||
|
|
|
||
|
|
float32 impulse = 0.0f;
|
||
|
|
if (mass > 0.0f)
|
||
|
|
{
|
||
|
|
impulse = -C / mass;
|
||
|
|
}
|
||
|
|
|
||
|
|
cA += m_mA * impulse * JvAC;
|
||
|
|
aA += m_iA * impulse * JwA;
|
||
|
|
cB += m_mB * impulse * JvBD;
|
||
|
|
aB += m_iB * impulse * JwB;
|
||
|
|
cC -= m_mC * impulse * JvAC;
|
||
|
|
aC -= m_iC * impulse * JwC;
|
||
|
|
cD -= m_mD * impulse * JvBD;
|
||
|
|
aD -= m_iD * impulse * JwD;
|
||
|
|
|
||
|
|
data.positions[m_indexA].c = cA;
|
||
|
|
data.positions[m_indexA].a = aA;
|
||
|
|
data.positions[m_indexB].c = cB;
|
||
|
|
data.positions[m_indexB].a = aB;
|
||
|
|
data.positions[m_indexC].c = cC;
|
||
|
|
data.positions[m_indexC].a = aC;
|
||
|
|
data.positions[m_indexD].c = cD;
|
||
|
|
data.positions[m_indexD].a = aD;
|
||
|
|
|
||
|
|
// TODO_ERIN not implemented
|
||
|
|
return linearError < b2_linearSlop;
|
||
|
|
}
|
||
|
|
|
||
|
|
b2Vec2 b2GearJoint::GetAnchorA() const
|
||
|
|
{
|
||
|
|
return m_bodyA->GetWorldPoint(m_localAnchorA);
|
||
|
|
}
|
||
|
|
|
||
|
|
b2Vec2 b2GearJoint::GetAnchorB() const
|
||
|
|
{
|
||
|
|
return m_bodyB->GetWorldPoint(m_localAnchorB);
|
||
|
|
}
|
||
|
|
|
||
|
|
b2Vec2 b2GearJoint::GetReactionForce(float32 inv_dt) const
|
||
|
|
{
|
||
|
|
b2Vec2 P = m_impulse * m_JvAC;
|
||
|
|
return inv_dt * P;
|
||
|
|
}
|
||
|
|
|
||
|
|
float32 b2GearJoint::GetReactionTorque(float32 inv_dt) const
|
||
|
|
{
|
||
|
|
float32 L = m_impulse * m_JwA;
|
||
|
|
return inv_dt * L;
|
||
|
|
}
|
||
|
|
|
||
|
|
void b2GearJoint::SetRatio(float32 ratio)
|
||
|
|
{
|
||
|
|
b2Assert(b2IsValid(ratio));
|
||
|
|
m_ratio = ratio;
|
||
|
|
}
|
||
|
|
|
||
|
|
float32 b2GearJoint::GetRatio() const
|
||
|
|
{
|
||
|
|
return m_ratio;
|
||
|
|
}
|
||
|
|
|
||
|
|
void b2GearJoint::Dump()
|
||
|
|
{
|
||
|
|
int32 indexA = m_bodyA->m_islandIndex;
|
||
|
|
int32 indexB = m_bodyB->m_islandIndex;
|
||
|
|
|
||
|
|
int32 index1 = m_joint1->m_index;
|
||
|
|
int32 index2 = m_joint2->m_index;
|
||
|
|
|
||
|
|
b2Log(" b2GearJointDef jd;\n");
|
||
|
|
b2Log(" jd.bodyA = bodies[%d];\n", indexA);
|
||
|
|
b2Log(" jd.bodyB = bodies[%d];\n", indexB);
|
||
|
|
b2Log(" jd.collideConnected = bool(%d);\n", m_collideConnected);
|
||
|
|
b2Log(" jd.joint1 = joints[%d];\n", index1);
|
||
|
|
b2Log(" jd.joint2 = joints[%d];\n", index2);
|
||
|
|
b2Log(" jd.ratio = %.15lef;\n", m_ratio);
|
||
|
|
b2Log(" joints[%d] = m_world->CreateJoint(&jd);\n", m_index);
|
||
|
|
}
|