420 lines
11 KiB
C++
420 lines
11 KiB
C++
|
/*
|
||
|
|
* Copyright (c) 2007-2011 Erin Catto http://www.box2d.org
|
||
|
|
*
|
||
|
|
* This software is provided 'as-is', without any express or implied
|
||
|
|
* warranty. In no event will the authors be held liable for any damages
|
||
|
|
* arising from the use of this software.
|
||
|
|
* Permission is granted to anyone to use this software for any purpose,
|
||
|
|
* including commercial applications, and to alter it and redistribute it
|
||
|
|
* freely, subject to the following restrictions:
|
||
|
|
* 1. The origin of this software must not be misrepresented; you must not
|
||
|
|
* claim that you wrote the original software. If you use this software
|
||
|
|
* in a product, an acknowledgment in the product documentation would be
|
||
|
|
* appreciated but is not required.
|
||
|
|
* 2. Altered source versions must be plainly marked as such, and must not be
|
||
|
|
* misrepresented as being the original software.
|
||
|
|
* 3. This notice may not be removed or altered from any source distribution.
|
||
|
|
*/
|
||
|
|
|
||
|
|
#include "Box2D/Dynamics/Joints/b2GearJoint.h"
|
||
|
|
#include "Box2D/Dynamics/Joints/b2RevoluteJoint.h"
|
||
|
|
#include "Box2D/Dynamics/Joints/b2PrismaticJoint.h"
|
||
|
|
#include "Box2D/Dynamics/b2Body.h"
|
||
|
|
#include "Box2D/Dynamics/b2TimeStep.h"
|
||
|
|
|
||
|
|
// Gear Joint:
|
||
|
|
// C0 = (coordinate1 + ratio * coordinate2)_initial
|
||
|
|
// C = (coordinate1 + ratio * coordinate2) - C0 = 0
|
||
|
|
// J = [J1 ratio * J2]
|
||
|
|
// K = J * invM * JT
|
||
|
|
// = J1 * invM1 * J1T + ratio * ratio * J2 * invM2 * J2T
|
||
|
|
//
|
||
|
|
// Revolute:
|
||
|
|
// coordinate = rotation
|
||
|
|
// Cdot = angularVelocity
|
||
|
|
// J = [0 0 1]
|
||
|
|
// K = J * invM * JT = invI
|
||
|
|
//
|
||
|
|
// Prismatic:
|
||
|
|
// coordinate = dot(p - pg, ug)
|
||
|
|
// Cdot = dot(v + cross(w, r), ug)
|
||
|
|
// J = [ug cross(r, ug)]
|
||
|
|
// K = J * invM * JT = invMass + invI * cross(r, ug)^2
|
||
|
|
|
||
|
|
b2GearJoint::b2GearJoint(const b2GearJointDef* def)
|
||
|
|
: b2Joint(def)
|
||
|
|
{
|
||
|
|
m_joint1 = def->joint1;
|
||
|
|
m_joint2 = def->joint2;
|
||
|
|
|
||
|
|
m_typeA = m_joint1->GetType();
|
||
|
|
m_typeB = m_joint2->GetType();
|
||
|
|
|
||
|
|
b2Assert(m_typeA == e_revoluteJoint || m_typeA == e_prismaticJoint);
|
||
|
|
b2Assert(m_typeB == e_revoluteJoint || m_typeB == e_prismaticJoint);
|
||
|
|
|
||
|
|
float32 coordinateA, coordinateB;
|
||
|
|
|
||
|
|
// TODO_ERIN there might be some problem with the joint edges in b2Joint.
|
||
|
|
|
||
|
|
m_bodyC = m_joint1->GetBodyA();
|
||
|
|
m_bodyA = m_joint1->GetBodyB();
|
||
|
|
|
||
|
|
// Get geometry of joint1
|
||
|
|
b2Transform xfA = m_bodyA->m_xf;
|
||
|
|
float32 aA = m_bodyA->m_sweep.a;
|
||
|
|
b2Transform xfC = m_bodyC->m_xf;
|
||
|
|
float32 aC = m_bodyC->m_sweep.a;
|
||
|
|
|
||
|
|
if (m_typeA == e_revoluteJoint)
|
||
|
|
{
|
||
|
|
b2RevoluteJoint* revolute = (b2RevoluteJoint*)def->joint1;
|
||
|
|
m_localAnchorC = revolute->m_localAnchorA;
|
||
|
|
m_localAnchorA = revolute->m_localAnchorB;
|
||
|
|
m_referenceAngleA = revolute->m_referenceAngle;
|
||
|
|
m_localAxisC.SetZero();
|
||
|
|
|
||
|
|
coordinateA = aA - aC - m_referenceAngleA;
|
||
|
|
}
|
||
|
|
else
|
||
|
|
{
|
||
|
|
b2PrismaticJoint* prismatic = (b2PrismaticJoint*)def->joint1;
|
||
|
|
m_localAnchorC = prismatic->m_localAnchorA;
|
||
|
|
m_localAnchorA = prismatic->m_localAnchorB;
|
||
|
|
m_referenceAngleA = prismatic->m_referenceAngle;
|
||
|
|
m_localAxisC = prismatic->m_localXAxisA;
|
||
|
|
|
||
|
|
b2Vec2 pC = m_localAnchorC;
|
||
|
|
b2Vec2 pA = b2MulT(xfC.q, b2Mul(xfA.q, m_localAnchorA) + (xfA.p - xfC.p));
|
||
|
|
coordinateA = b2Dot(pA - pC, m_localAxisC);
|
||
|
|
}
|
||
|
|
|
||
|
|
m_bodyD = m_joint2->GetBodyA();
|
||
|
|
m_bodyB = m_joint2->GetBodyB();
|
||
|
|
|
||
|
|
// Get geometry of joint2
|
||
|
|
b2Transform xfB = m_bodyB->m_xf;
|
||
|
|
float32 aB = m_bodyB->m_sweep.a;
|
||
|
|
b2Transform xfD = m_bodyD->m_xf;
|
||
|
|
float32 aD = m_bodyD->m_sweep.a;
|
||
|
|
|
||
|
|
if (m_typeB == e_revoluteJoint)
|
||
|
|
{
|
||
|
|
b2RevoluteJoint* revolute = (b2RevoluteJoint*)def->joint2;
|
||
|
|
m_localAnchorD = revolute->m_localAnchorA;
|
||
|
|
m_localAnchorB = revolute->m_localAnchorB;
|
||
|
|
m_referenceAngleB = revolute->m_referenceAngle;
|
||
|
|
m_localAxisD.SetZero();
|
||
|
|
|
||
|
|
coordinateB = aB - aD - m_referenceAngleB;
|
||
|
|
}
|
||
|
|
else
|
||
|
|
{
|
||
|
|
b2PrismaticJoint* prismatic = (b2PrismaticJoint*)def->joint2;
|
||
|
|
m_localAnchorD = prismatic->m_localAnchorA;
|
||
|
|
m_localAnchorB = prismatic->m_localAnchorB;
|
||
|
|
m_referenceAngleB = prismatic->m_referenceAngle;
|
||
|
|
m_localAxisD = prismatic->m_localXAxisA;
|
||
|
|
|
||
|
|
b2Vec2 pD = m_localAnchorD;
|
||
|
|
b2Vec2 pB = b2MulT(xfD.q, b2Mul(xfB.q, m_localAnchorB) + (xfB.p - xfD.p));
|
||
|
|
coordinateB = b2Dot(pB - pD, m_localAxisD);
|
||
|
|
}
|
||
|
|
|
||
|
|
m_ratio = def->ratio;
|
||
|
|
|
||
|
|
m_constant = coordinateA + m_ratio * coordinateB;
|
||
|
|
|
||
|
|
m_impulse = 0.0f;
|
||
|
|
}
|
||
|
|
|
||
|
|
void b2GearJoint::InitVelocityConstraints(const b2SolverData& data)
|
||
|
|
{
|
||
|
|
m_indexA = m_bodyA->m_islandIndex;
|
||
|
|
m_indexB = m_bodyB->m_islandIndex;
|
||
|
|
m_indexC = m_bodyC->m_islandIndex;
|
||
|
|
m_indexD = m_bodyD->m_islandIndex;
|
||
|
|
m_lcA = m_bodyA->m_sweep.localCenter;
|
||
|
|
m_lcB = m_bodyB->m_sweep.localCenter;
|
||
|
|
m_lcC = m_bodyC->m_sweep.localCenter;
|
||
|
|
m_lcD = m_bodyD->m_sweep.localCenter;
|
||
|
|
m_mA = m_bodyA->m_invMass;
|
||
|
|
m_mB = m_bodyB->m_invMass;
|
||
|
|
m_mC = m_bodyC->m_invMass;
|
||
|
|
m_mD = m_bodyD->m_invMass;
|
||
|
|
m_iA = m_bodyA->m_invI;
|
||
|
|
m_iB = m_bodyB->m_invI;
|
||
|
|
m_iC = m_bodyC->m_invI;
|
||
|
|
m_iD = m_bodyD->m_invI;
|
||
|
|
|
||
|
|
float32 aA = data.positions[m_indexA].a;
|
||
|
|
b2Vec2 vA = data.velocities[m_indexA].v;
|
||
|
|
float32 wA = data.velocities[m_indexA].w;
|
||
|
|
|
||
|
|
float32 aB = data.positions[m_indexB].a;
|
||
|
|
b2Vec2 vB = data.velocities[m_indexB].v;
|
||
|
|
float32 wB = data.velocities[m_indexB].w;
|
||
|
|
|
||
|
|
float32 aC = data.positions[m_indexC].a;
|
||
|
|
b2Vec2 vC = data.velocities[m_indexC].v;
|
||
|
|
float32 wC = data.velocities[m_indexC].w;
|
||
|
|
|
||
|
|
float32 aD = data.positions[m_indexD].a;
|
||
|
|
b2Vec2 vD = data.velocities[m_indexD].v;
|
||
|
|
float32 wD = data.velocities[m_indexD].w;
|
||
|
|
|
||
|
|
b2Rot qA(aA), qB(aB), qC(aC), qD(aD);
|
||
|
|
|
||
|
|
m_mass = 0.0f;
|
||
|
|
|
||
|
|
if (m_typeA == e_revoluteJoint)
|
||
|
|
{
|
||
|
|
m_JvAC.SetZero();
|
||
|
|
m_JwA = 1.0f;
|
||
|
|
m_JwC = 1.0f;
|
||
|
|
m_mass += m_iA + m_iC;
|
||
|
|
}
|
||
|
|
else
|
||
|
|
{
|
||
|
|
b2Vec2 u = b2Mul(qC, m_localAxisC);
|
||
|
|
b2Vec2 rC = b2Mul(qC, m_localAnchorC - m_lcC);
|
||
|
|
b2Vec2 rA = b2Mul(qA, m_localAnchorA - m_lcA);
|
||
|
|
m_JvAC = u;
|
||
|
|
m_JwC = b2Cross(rC, u);
|
||
|
|
m_JwA = b2Cross(rA, u);
|
||
|
|
m_mass += m_mC + m_mA + m_iC * m_JwC * m_JwC + m_iA * m_JwA * m_JwA;
|
||
|
|
}
|
||
|
|
|
||
|
|
if (m_typeB == e_revoluteJoint)
|
||
|
|
{
|
||
|
|
m_JvBD.SetZero();
|
||
|
|
m_JwB = m_ratio;
|
||
|
|
m_JwD = m_ratio;
|
||
|
|
m_mass += m_ratio * m_ratio * (m_iB + m_iD);
|
||
|
|
}
|
||
|
|
else
|
||
|
|
{
|
||
|
|
b2Vec2 u = b2Mul(qD, m_localAxisD);
|
||
|
|
b2Vec2 rD = b2Mul(qD, m_localAnchorD - m_lcD);
|
||
|
|
b2Vec2 rB = b2Mul(qB, m_localAnchorB - m_lcB);
|
||
|
|
m_JvBD = m_ratio * u;
|
||
|
|
m_JwD = m_ratio * b2Cross(rD, u);
|
||
|
|
m_JwB = m_ratio * b2Cross(rB, u);
|
||
|
|
m_mass += m_ratio * m_ratio * (m_mD + m_mB) + m_iD * m_JwD * m_JwD + m_iB * m_JwB * m_JwB;
|
||
|
|
}
|
||
|
|
|
||
|
|
// Compute effective mass.
|
||
|
|
m_mass = m_mass > 0.0f ? 1.0f / m_mass : 0.0f;
|
||
|
|
|
||
|
|
if (data.step.warmStarting)
|
||
|
|
{
|
||
|
|
vA += (m_mA * m_impulse) * m_JvAC;
|
||
|
|
wA += m_iA * m_impulse * m_JwA;
|
||
|
|
vB += (m_mB * m_impulse) * m_JvBD;
|
||
|
|
wB += m_iB * m_impulse * m_JwB;
|
||
|
|
vC -= (m_mC * m_impulse) * m_JvAC;
|
||
|
|
wC -= m_iC * m_impulse * m_JwC;
|
||
|
|
vD -= (m_mD * m_impulse) * m_JvBD;
|
||
|
|
wD -= m_iD * m_impulse * m_JwD;
|
||
|
|
}
|
||
|
|
else
|
||
|
|
{
|
||
|
|
m_impulse = 0.0f;
|
||
|
|
}
|
||
|
|
|
||
|
|
data.velocities[m_indexA].v = vA;
|
||
|
|
data.velocities[m_indexA].w = wA;
|
||
|
|
data.velocities[m_indexB].v = vB;
|
||
|
|
data.velocities[m_indexB].w = wB;
|
||
|
|
data.velocities[m_indexC].v = vC;
|
||
|
|
data.velocities[m_indexC].w = wC;
|
||
|
|
data.velocities[m_indexD].v = vD;
|
||
|
|
data.velocities[m_indexD].w = wD;
|
||
|
|
}
|
||
|
|
|
||
|
|
void b2GearJoint::SolveVelocityConstraints(const b2SolverData& data)
|
||
|
|
{
|
||
|
|
b2Vec2 vA = data.velocities[m_indexA].v;
|
||
|
|
float32 wA = data.velocities[m_indexA].w;
|
||
|
|
b2Vec2 vB = data.velocities[m_indexB].v;
|
||
|
|
float32 wB = data.velocities[m_indexB].w;
|
||
|
|
b2Vec2 vC = data.velocities[m_indexC].v;
|
||
|
|
float32 wC = data.velocities[m_indexC].w;
|
||
|
|
b2Vec2 vD = data.velocities[m_indexD].v;
|
||
|
|
float32 wD = data.velocities[m_indexD].w;
|
||
|
|
|
||
|
|
float32 Cdot = b2Dot(m_JvAC, vA - vC) + b2Dot(m_JvBD, vB - vD);
|
||
|
|
Cdot += (m_JwA * wA - m_JwC * wC) + (m_JwB * wB - m_JwD * wD);
|
||
|
|
|
||
|
|
float32 impulse = -m_mass * Cdot;
|
||
|
|
m_impulse += impulse;
|
||
|
|
|
||
|
|
vA += (m_mA * impulse) * m_JvAC;
|
||
|
|
wA += m_iA * impulse * m_JwA;
|
||
|
|
vB += (m_mB * impulse) * m_JvBD;
|
||
|
|
wB += m_iB * impulse * m_JwB;
|
||
|
|
vC -= (m_mC * impulse) * m_JvAC;
|
||
|
|
wC -= m_iC * impulse * m_JwC;
|
||
|
|
vD -= (m_mD * impulse) * m_JvBD;
|
||
|
|
wD -= m_iD * impulse * m_JwD;
|
||
|
|
|
||
|
|
data.velocities[m_indexA].v = vA;
|
||
|
|
data.velocities[m_indexA].w = wA;
|
||
|
|
data.velocities[m_indexB].v = vB;
|
||
|
|
data.velocities[m_indexB].w = wB;
|
||
|
|
data.velocities[m_indexC].v = vC;
|
||
|
|
data.velocities[m_indexC].w = wC;
|
||
|
|
data.velocities[m_indexD].v = vD;
|
||
|
|
data.velocities[m_indexD].w = wD;
|
||
|
|
}
|
||
|
|
|
||
|
|
bool b2GearJoint::SolvePositionConstraints(const b2SolverData& data)
|
||
|
|
{
|
||
|
|
b2Vec2 cA = data.positions[m_indexA].c;
|
||
|
|
float32 aA = data.positions[m_indexA].a;
|
||
|
|
b2Vec2 cB = data.positions[m_indexB].c;
|
||
|
|
float32 aB = data.positions[m_indexB].a;
|
||
|
|
b2Vec2 cC = data.positions[m_indexC].c;
|
||
|
|
float32 aC = data.positions[m_indexC].a;
|
||
|
|
b2Vec2 cD = data.positions[m_indexD].c;
|
||
|
|
float32 aD = data.positions[m_indexD].a;
|
||
|
|
|
||
|
|
b2Rot qA(aA), qB(aB), qC(aC), qD(aD);
|
||
|
|
|
||
|
|
float32 linearError = 0.0f;
|
||
|
|
|
||
|
|
float32 coordinateA, coordinateB;
|
||
|
|
|
||
|
|
b2Vec2 JvAC, JvBD;
|
||
|
|
float32 JwA, JwB, JwC, JwD;
|
||
|
|
float32 mass = 0.0f;
|
||
|
|
|
||
|
|
if (m_typeA == e_revoluteJoint)
|
||
|
|
{
|
||
|
|
JvAC.SetZero();
|
||
|
|
JwA = 1.0f;
|
||
|
|
JwC = 1.0f;
|
||
|
|
mass += m_iA + m_iC;
|
||
|
|
|
||
|
|
coordinateA = aA - aC - m_referenceAngleA;
|
||
|
|
}
|
||
|
|
else
|
||
|
|
{
|
||
|
|
b2Vec2 u = b2Mul(qC, m_localAxisC);
|
||
|
|
b2Vec2 rC = b2Mul(qC, m_localAnchorC - m_lcC);
|
||
|
|
b2Vec2 rA = b2Mul(qA, m_localAnchorA - m_lcA);
|
||
|
|
JvAC = u;
|
||
|
|
JwC = b2Cross(rC, u);
|
||
|
|
JwA = b2Cross(rA, u);
|
||
|
|
mass += m_mC + m_mA + m_iC * JwC * JwC + m_iA * JwA * JwA;
|
||
|
|
|
||
|
|
b2Vec2 pC = m_localAnchorC - m_lcC;
|
||
|
|
b2Vec2 pA = b2MulT(qC, rA + (cA - cC));
|
||
|
|
coordinateA = b2Dot(pA - pC, m_localAxisC);
|
||
|
|
}
|
||
|
|
|
||
|
|
if (m_typeB == e_revoluteJoint)
|
||
|
|
{
|
||
|
|
JvBD.SetZero();
|
||
|
|
JwB = m_ratio;
|
||
|
|
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);
|
||
|
|
}
|