public override void initVelocityConstraints(SolverData data) { m_indexA = m_bodyA.m_islandIndex; m_indexB = m_bodyB.m_islandIndex; m_localCenterA.set(m_bodyA.m_sweep.localCenter); m_localCenterB.set(m_bodyB.m_sweep.localCenter); m_invMassA = m_bodyA.m_invMass; m_invMassB = m_bodyB.m_invMass; m_invIA = m_bodyA.m_invI; m_invIB = m_bodyB.m_invI; // Vec2 cA = data.positions[m_indexA].c; double aA = data.positions[m_indexA].a; Vec2 vA = data.velocities[m_indexA].v; double wA = data.velocities[m_indexA].w; // Vec2 cB = data.positions[m_indexB].c; double aB = data.positions[m_indexB].a; Vec2 vB = data.velocities[m_indexB].v; double wB = data.velocities[m_indexB].w; Rot qA = pool.popRot(); Rot qB = pool.popRot(); Vec2 temp = pool.popVec2(); qA.set(aA); qB.set(aB); // Compute the effective masses. Rot.mulToOutUnsafe(qA, temp.set(m_localAnchorA).subLocal(m_localCenterA), m_rA); Rot.mulToOutUnsafe(qB, temp.set(m_localAnchorB).subLocal(m_localCenterB), m_rB); // J = [-I -r1_skew I r2_skew] // [ 0 -1 0 1] // r_skew = [-ry; rx] // Matlab // K = [ mA+r1y^2*iA+mB+r2y^2*iB, -r1y*iA*r1x-r2y*iB*r2x, -r1y*iA-r2y*iB] // [ -r1y*iA*r1x-r2y*iB*r2x, mA+r1x^2*iA+mB+r2x^2*iB, r1x*iA+r2x*iB] // [ -r1y*iA-r2y*iB, r1x*iA+r2x*iB, iA+iB] double mA = m_invMassA, mB = m_invMassB; double iA = m_invIA, iB = m_invIB; Mat33 K = pool.popMat33(); K.ex.x = mA + mB + m_rA.y * m_rA.y * iA + m_rB.y * m_rB.y * iB; K.ey.x = -m_rA.y * m_rA.x * iA - m_rB.y * m_rB.x * iB; K.ez.x = -m_rA.y * iA - m_rB.y * iB; K.ex.y = K.ey.x; K.ey.y = mA + mB + m_rA.x * m_rA.x * iA + m_rB.x * m_rB.x * iB; K.ez.y = m_rA.x * iA + m_rB.x * iB; K.ex.z = K.ez.x; K.ey.z = K.ez.y; K.ez.z = iA + iB; if (m_frequencyHz > 0.0d) { K.getInverse22(m_mass); double invM = iA + iB; double m = invM > 0.0d ? 1.0d / invM : 0.0d; double C = aB - aA - m_referenceAngle; // Frequency double omega = 2.0d * MathUtils.PI * m_frequencyHz; // Damping coefficient double d = 2.0d * m * m_dampingRatio * omega; // Spring stiffness double k = m * omega * omega; // magic formulas double h = data.step.dt; m_gamma = h * (d + h * k); m_gamma = m_gamma != 0.0d ? 1.0d / m_gamma : 0.0d; m_bias = C * h * k * m_gamma; invM += m_gamma; m_mass.ez.z = invM != 0.0d ? 1.0d / invM : 0.0d; } else { K.getSymInverse33(m_mass); m_gamma = 0.0d; m_bias = 0.0d; } if (data.step.warmStarting) { Vec2 P = pool.popVec2(); // Scale impulses to support a variable time step. m_impulse.mulLocal(data.step.dtRatio); P.set(m_impulse.x, m_impulse.y); vA.x -= mA * P.x; vA.y -= mA * P.y; wA -= iA * (Vec2.cross(m_rA, P) + m_impulse.z); vB.x += mB * P.x; vB.y += mB * P.y; wB += iB * (Vec2.cross(m_rB, P) + m_impulse.z); pool.pushVec2(1); } else { m_impulse.setZero(); } // data.velocities[m_indexA].v.set(vA); data.velocities[m_indexA].w = wA; // data.velocities[m_indexB].v.set(vB); data.velocities[m_indexB].w = wB; pool.pushVec2(1); pool.pushRot(2); pool.pushMat33(1); }