void b2WeldJoint::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;
float32 mA = m_invMassA, mB = m_invMassB;
float32 iA = m_invIA, iB = m_invIB;
if (m_frequencyHz > 0.0f)
{
float32 Cdot2 = wB - wA;
float32 impulse2 = -m_mass.ez.z * (Cdot2 + m_bias + m_gamma * m_impulse.z);
m_impulse.z += impulse2;
wA -= iA * impulse2;
wB += iB * impulse2;
b2Vec2 Cdot1 = vB + b2Cross(wB, m_rB) - vA - b2Cross(wA, m_rA);
b2Vec2 impulse1 = -b2Mul22(m_mass, Cdot1);
m_impulse.x += impulse1.x;
m_impulse.y += impulse1.y;
b2Vec2 P = impulse1;
vA -= mA * P;
wA -= iA * b2Cross(m_rA, P);
vB += mB * P;
wB += iB * b2Cross(m_rB, P);
}
else
{
b2Vec2 Cdot1 = vB + b2Cross(wB, m_rB) - vA - b2Cross(wA, m_rA);
float32 Cdot2 = wB - wA;
b2Vec3 Cdot(Cdot1.x, Cdot1.y, Cdot2);
b2Vec3 impulse = -b2Mul(m_mass, Cdot);
m_impulse += impulse;
b2Vec2 P(impulse.x, impulse.y);
vA -= mA * P;
wA -= iA * (b2Cross(m_rA, P) + impulse.z);
vB += mB * P;
wB += iB * (b2Cross(m_rB, P) + impulse.z);
}
data.velocities[m_indexA].v = vA;
data.velocities[m_indexA].w = wA;
data.velocities[m_indexB].v = vB;
data.velocities[m_indexB].w = wB;
}
void b2PrismaticJoint::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;
float32 mA = m_invMassA, mB = m_invMassB;
float32 iA = m_invIA, iB = m_invIB;
// Solve linear motor constraint.
if (m_enableMotor && m_limitState != e_equalLimits)
{
float32 Cdot = b2Dot(m_axis, vB - vA) + m_a2 * wB - m_a1 * wA;
float32 impulse = m_motorMass * (m_motorSpeed - Cdot);
float32 oldImpulse = m_motorImpulse;
float32 maxImpulse = data.step.dt * m_maxMotorForce;
m_motorImpulse = b2Clamp(m_motorImpulse + impulse, -maxImpulse, maxImpulse);
impulse = m_motorImpulse - oldImpulse;
b2Vec2 P = impulse * m_axis;
float32 LA = impulse * m_a1;
float32 LB = impulse * m_a2;
vA -= mA * P;
wA -= iA * LA;
vB += mB * P;
wB += iB * LB;
}
b2Vec2 Cdot1;
Cdot1.x = b2Dot(m_perp, vB - vA) + m_s2 * wB - m_s1 * wA;
Cdot1.y = wB - wA;
if (m_enableLimit && m_limitState != e_inactiveLimit)
{
// Solve prismatic and limit constraint in block form.
float32 Cdot2;
Cdot2 = b2Dot(m_axis, vB - vA) + m_a2 * wB - m_a1 * wA;
b2Vec3 Cdot(Cdot1.x, Cdot1.y, Cdot2);
b2Vec3 f1 = m_impulse;
b2Vec3 df = m_K.Solve33(-Cdot);
m_impulse += df;
if (m_limitState == e_atLowerLimit)
{
m_impulse.z = b2Max(m_impulse.z, 0.0f);
}
else if (m_limitState == e_atUpperLimit)
{
m_impulse.z = b2Min(m_impulse.z, 0.0f);
}
// f2(1:2) = invK(1:2,1:2) * (-Cdot(1:2) - K(1:2,3) * (f2(3) - f1(3))) + f1(1:2)
b2Vec2 b = -Cdot1 - (m_impulse.z - f1.z) * b2Vec2(m_K.ez.x, m_K.ez.y);
b2Vec2 f2r = m_K.Solve22(b) + b2Vec2(f1.x, f1.y);
m_impulse.x = f2r.x;
m_impulse.y = f2r.y;
df = m_impulse - f1;
b2Vec2 P = df.x * m_perp + df.z * m_axis;
float32 LA = df.x * m_s1 + df.y + df.z * m_a1;
float32 LB = df.x * m_s2 + df.y + df.z * m_a2;
vA -= mA * P;
wA -= iA * LA;
vB += mB * P;
wB += iB * LB;
}
else
{
// Limit is inactive, just solve the prismatic constraint in block form.
b2Vec2 df = m_K.Solve22(-Cdot1);
m_impulse.x += df.x;
m_impulse.y += df.y;
b2Vec2 P = df.x * m_perp;
float32 LA = df.x * m_s1 + df.y;
float32 LB = df.x * m_s2 + df.y;
vA -= mA * P;
wA -= iA * LA;
vB += mB * P;
wB += iB * LB;
b2Vec2 Cdot10 = Cdot1;
Cdot1.x = b2Dot(m_perp, vB - vA) + m_s2 * wB - m_s1 * wA;
Cdot1.y = wB - wA;
if (b2Abs(Cdot1.x) > 0.01f || b2Abs(Cdot1.y) > 0.01f)
{
b2Vec2 test = b2Mul22(m_K, df);
Cdot1.x += 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;
}
