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C++ qB函数代码示例

原作者: [db:作者] 来自: [db:来源] 收藏 邀请

本文整理汇总了C++中qB函数的典型用法代码示例。如果您正苦于以下问题：C++ qB函数的具体用法？C++ qB怎么用？C++ qB使用的例子？那么恭喜您, 这里精选的函数代码示例或许可以为您提供帮助。



在下文中一共展示了qB函数的10个代码示例，这些例子默认根据受欢迎程度排序。您可以为喜欢或者感觉有用的代码点赞，您的评价将有助于我们的系统推荐出更棒的C++代码示例。

示例1: qA

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;
}
开发者ID:Brodjaga，项目名称:libgdx-cpp，代码行数:98，代码来源:b2GearJoint.cpp


示例2: qA

void b2RopeJoint::InitVelocityConstraints(const b2SolverData& data)
{
    m_indexA = m_bodyA->m_islandIndex;
    m_indexB = m_bodyB->m_islandIndex;
    m_localCenterA = m_bodyA->m_sweep.localCenter;
    m_localCenterB = 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;

    b2Vec2 cA = data.positions[m_indexA].c;
    float32 aA = data.positions[m_indexA].a;
    b2Vec2 vA = data.velocities[m_indexA].v;
    float32 wA = data.velocities[m_indexA].w;

    b2Vec2 cB = data.positions[m_indexB].c;
    float32 aB = data.positions[m_indexB].a;
    b2Vec2 vB = data.velocities[m_indexB].v;
    float32 wB = data.velocities[m_indexB].w;

    b2Rot qA(aA), qB(aB);

    m_rA = b2Mul(qA, m_localAnchorA - m_localCenterA);
    m_rB = b2Mul(qB, m_localAnchorB - m_localCenterB);
    m_u = cB + m_rB - cA - m_rA;

    m_length = m_u.Length();

    float32 C = m_length - m_maxLength;
    if (C > 0.0f)
    {
        m_state = e_atUpperLimit;
    }
    else
    {
        m_state = e_inactiveLimit;
    }

    if (m_length > b2_linearSlop)
    {
        m_u *= 1.0f / m_length;
    }
    else
    {
        m_u.SetZero();
        m_mass = 0.0f;
        m_impulse = 0.0f;
        return;
    }

    // Compute effective mass.
    float32 crA = b2Cross(m_rA, m_u);
    float32 crB = b2Cross(m_rB, m_u);
    float32 invMass = m_invMassA + m_invIA * crA * crA + m_invMassB + m_invIB * crB * crB;

    m_mass = invMass != 0.0f ? 1.0f / invMass : 0.0f;

    if (data.step.warmStarting)
    {
        // Scale the impulse to support a variable time step.
        m_impulse *= data.step.dtRatio;

        b2Vec2 P = m_impulse * m_u;
        vA -= m_invMassA * P;
        wA -= m_invIA * b2Cross(m_rA, P);
        vB += m_invMassB * P;
        wB += m_invIB * b2Cross(m_rB, P);
    }
    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;
}
开发者ID:GhostSoar，项目名称:Cocos2dWindows，代码行数:79，代码来源:b2RopeJoint.cpp


示例3: qA

bool b2PrismaticJoint::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;

    b2Rot qA(aA), qB(aB);

    float32 mA = m_invMassA, mB = m_invMassB;
    float32 iA = m_invIA, iB = m_invIB;

    // Compute fresh Jacobians
    b2Vec2 rA = b2Mul(qA, m_localAnchorA - m_localCenterA);
    b2Vec2 rB = b2Mul(qB, m_localAnchorB - m_localCenterB);
    b2Vec2 d = cB + rB - cA - rA;

    b2Vec2 axis = b2Mul(qA, m_localXAxisA);
    float32 a1 = b2Cross(d + rA, axis);
    float32 a2 = b2Cross(rB, axis);
    b2Vec2 perp = b2Mul(qA, m_localYAxisA);

    float32 s1 = b2Cross(d + rA, perp);
    float32 s2 = b2Cross(rB, perp);

    b2Vec3 impulse;
    b2Vec2 C1;
    C1.x = b2Dot(perp, d);
    C1.y = aB - aA - m_referenceAngle;

    float32 linearError = b2Abs(C1.x);
    float32 angularError = b2Abs(C1.y);

    bool active = false;
    float32 C2 = 0.0f;
    if (m_enableLimit)
    {
        float32 translation = b2Dot(axis, d);
        if (b2Abs(m_upperTranslation - m_lowerTranslation) < 2.0f * b2_linearSlop)
        {
            // Prevent large angular corrections
            C2 = b2Clamp(translation, -b2_maxLinearCorrection, b2_maxLinearCorrection);
            linearError = b2Max(linearError, b2Abs(translation));
            active = true;
        }
        else if (translation <= m_lowerTranslation)
        {
            // Prevent large linear corrections and allow some slop.
            C2 = b2Clamp(translation - m_lowerTranslation + b2_linearSlop, -b2_maxLinearCorrection, 0.0f);
            linearError = b2Max(linearError, m_lowerTranslation - translation);
            active = true;
        }
        else if (translation >= m_upperTranslation)
        {
            // Prevent large linear corrections and allow some slop.
            C2 = b2Clamp(translation - m_upperTranslation - b2_linearSlop, 0.0f, b2_maxLinearCorrection);
            linearError = b2Max(linearError, translation - m_upperTranslation);
            active = true;
        }
    }

    if (active)
    {
        float32 k11 = mA + mB + iA * s1 * s1 + iB * s2 * s2;
        float32 k12 = iA * s1 + iB * s2;
        float32 k13 = iA * s1 * a1 + iB * s2 * a2;
        float32 k22 = iA + iB;
        if (k22 == 0.0f)
        {
            // For fixed rotation
            k22 = 1.0f;
        }
        float32 k23 = iA * a1 + iB * a2;
        float32 k33 = mA + mB + iA * a1 * a1 + iB * a2 * a2;

        b2Mat33 K;
        K.ex.Set(k11, k12, k13);
        K.ey.Set(k12, k22, k23);
        K.ez.Set(k13, k23, k33);

        b2Vec3 C;
        C.x = C1.x;
        C.y = C1.y;
        C.z = C2;

        impulse = K.Solve33(-C);
    }
    else
    {
        float32 k11 = mA + mB + iA * s1 * s1 + iB * s2 * s2;
        float32 k12 = iA * s1 + iB * s2;
        float32 k22 = iA + iB;
        if (k22 == 0.0f)
        {
            k22 = 1.0f;
        }

        b2Mat22 K;
        K.ex.Set(k11, k12);
        K.ey.Set(k12, k22);
//.........这里部分代码省略.........
开发者ID:GhostSoar，项目名称:Cocos2dWindows，代码行数:101，代码来源:b2PrismaticJoint.cpp


示例4: qA

void b2DistanceJoint::InitVelocityConstraints(const b2SolverData& data)
{
	m_indexA = m_bodyA->m_islandIndex;
	m_indexB = m_bodyB->m_islandIndex;
	m_localCenterA = m_bodyA->m_sweep.localCenter;
	m_localCenterB = 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;

	b2Vec2 cA = data.positions[m_indexA].c;
	float32 aA = data.positions[m_indexA].a;
	b2Vec2 vA = data.velocities[m_indexA].v;
	float32 wA = data.velocities[m_indexA].w;

	b2Vec2 cB = data.positions[m_indexB].c;
	float32 aB = data.positions[m_indexB].a;
	b2Vec2 vB = data.velocities[m_indexB].v;
	float32 wB = data.velocities[m_indexB].w;

	b2Rot qA(aA), qB(aB);

	m_rA = b2Mul(qA, m_localAnchorA - m_localCenterA);
	m_rB = b2Mul(qB, m_localAnchorB - m_localCenterB);
	m_u = cB + m_rB - cA - m_rA;

	// Handle singularity.
	float32 length = m_u.Length();
	if (length > b2_linearSlop)
	{
		m_u *= 1.0f / length;
	}
	else
	{
		m_u.Set(0.0f, 0.0f);
	}

	float32 crAu = b2Cross(m_rA, m_u);
	float32 crBu = b2Cross(m_rB, m_u);
	float32 invMass = m_invMassA + m_invIA * crAu * crAu + m_invMassB + m_invIB * crBu * crBu;

	// Compute the effective mass matrix.
	m_mass = invMass != 0.0f ? 1.0f / invMass : 0.0f;

	if (m_frequencyHz > 0.0f)
	{
		float32 C = length - m_length;

		// Frequency
		float32 omega = 2.0f * b2_pi * m_frequencyHz;

		// Damping coefficient
		float32 d = 2.0f * m_mass * m_dampingRatio * omega;

		// Spring stiffness
		float32 k = m_mass * omega * omega;

		// magic formulas
		float32 h = data.step.dt;
		m_gamma = h * (d + h * k);
		m_gamma = m_gamma != 0.0f ? 1.0f / m_gamma : 0.0f;
		m_bias = C * h * k * m_gamma;

		invMass += m_gamma;
		m_mass = invMass != 0.0f ? 1.0f / invMass : 0.0f;
	}
	else
	{
		m_gamma = 0.0f;
		m_bias = 0.0f;
	}

	if (data.step.warmStarting)
	{
		// Scale the impulse to support a variable time step.
		m_impulse *= data.step.dtRatio;

		b2Vec2 P = m_impulse * m_u;
		vA -= m_invMassA * P;
		wA -= m_invIA * b2Cross(m_rA, P);
		vB += m_invMassB * P;
		wB += m_invIB * b2Cross(m_rB, P);
	}
	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;
}
开发者ID:0302zq，项目名称:libgdx，代码行数:94，代码来源:b2DistanceJoint.cpp


示例5: qA

bool b2WeldJoint::SolvePositionConstraints(const b2SolverData& data)
{
	b2Vec2 cA = data.positions[m_indexA].c;
	float aA = data.positions[m_indexA].a;
	b2Vec2 cB = data.positions[m_indexB].c;
	float aB = data.positions[m_indexB].a;

	b2Rot qA(aA), qB(aB);

	float mA = m_invMassA, mB = m_invMassB;
	float iA = m_invIA, iB = m_invIB;

	b2Vec2 rA = b2Mul(qA, m_localAnchorA - m_localCenterA);
	b2Vec2 rB = b2Mul(qB, m_localAnchorB - m_localCenterB);

	float positionError, angularError;

	b2Mat33 K;
	K.ex.x = mA + mB + rA.y * rA.y * iA + rB.y * rB.y * iB;
	K.ey.x = -rA.y * rA.x * iA - rB.y * rB.x * iB;
	K.ez.x = -rA.y * iA - rB.y * iB;
	K.ex.y = K.ey.x;
	K.ey.y = mA + mB + rA.x * rA.x * iA + rB.x * rB.x * iB;
	K.ez.y = rA.x * iA + rB.x * iB;
	K.ex.z = K.ez.x;
	K.ey.z = K.ez.y;
	K.ez.z = iA + iB;

	if (m_frequencyHz > 0.0f)
	{
		b2Vec2 C1 =  cB + rB - cA - rA;

		positionError = C1.Length();
		angularError = 0.0f;

		b2Vec2 P = -K.Solve22(C1);

		cA -= mA * P;
		aA -= iA * b2Cross(rA, P);

		cB += mB * P;
		aB += iB * b2Cross(rB, P);
	}
	else
	{
		b2Vec2 C1 =  cB + rB - cA - rA;
		float C2 = aB - aA - m_referenceAngle;

		positionError = C1.Length();
		angularError = b2Abs(C2);

		b2Vec3 C(C1.x, C1.y, C2);
	
		b2Vec3 impulse = -K.Solve33(C);
		b2Vec2 P(impulse.x, impulse.y);

		cA -= mA * P;
		aA -= iA * (b2Cross(rA, P) + impulse.z);

		cB += mB * P;
		aB += iB * (b2Cross(rB, P) + impulse.z);
	}

	data.positions[m_indexA].c = cA;
	data.positions[m_indexA].a = aA;
	data.positions[m_indexB].c = cB;
	data.positions[m_indexB].a = aB;

	return positionError <= b2_linearSlop && angularError <= b2_angularSlop;
}
开发者ID:Epidilius，项目名称:PhysicsHackAndSlash，代码行数:70，代码来源:b2WeldJoint.cpp


示例6: qA

void b2MotorJoint::InitVelocityConstraints(const b2SolverData& data)
{
	m_indexA = m_bodyA->m_islandIndex;
	m_indexB = m_bodyB->m_islandIndex;
	m_localCenterA = m_bodyA->m_sweep.localCenter;
	m_localCenterB = 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;

	b2Vec2 cA = data.positions[m_indexA].c;
	float32 aA = data.positions[m_indexA].a;
	b2Vec2 vA = data.velocities[m_indexA].v;
	float32 wA = data.velocities[m_indexA].w;

	b2Vec2 cB = data.positions[m_indexB].c;
	float32 aB = data.positions[m_indexB].a;
	b2Vec2 vB = data.velocities[m_indexB].v;
	float32 wB = data.velocities[m_indexB].w;

	b2Rot qA(aA), qB(aB);

	// Compute the effective mass matrix.
	m_rA = b2Mul(qA, -m_localCenterA);
	m_rB = b2Mul(qB, -m_localCenterB);

	// 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]

	float32 mA = m_invMassA, mB = m_invMassB;
	float32 iA = m_invIA, iB = m_invIB;

	b2Mat22 K;
	K.ex.x = mA + mB + iA * m_rA.y * m_rA.y + iB * m_rB.y * m_rB.y;
	K.ex.y = -iA * m_rA.x * m_rA.y - iB * m_rB.x * m_rB.y;
	K.ey.x = K.ex.y;
	K.ey.y = mA + mB + iA * m_rA.x * m_rA.x + iB * m_rB.x * m_rB.x;

	m_linearMass = K.GetInverse();

	m_angularMass = iA + iB;
	if (m_angularMass > 0.0f)
	{
		m_angularMass = 1.0f / m_angularMass;
	}

	m_linearError = cB + m_rB - cA - m_rA - b2Mul(qA, m_linearOffset);
	m_angularError = aB - aA - m_angularOffset;

	if (data.step.warmStarting)
	{
		// Scale impulses to support a variable time step.
		m_linearImpulse *= data.step.dtRatio;
		m_angularImpulse *= data.step.dtRatio;

		b2Vec2 P(m_linearImpulse.x, m_linearImpulse.y);
		vA -= mA * P;
		wA -= iA * (b2Cross(m_rA, P) + m_angularImpulse);
		vB += mB * P;
		wB += iB * (b2Cross(m_rB, P) + m_angularImpulse);
	}
	else
	{
		m_linearImpulse.SetZero();
		m_angularImpulse = 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;
}
开发者ID:RyunosukeOno，项目名称:rayjack，代码行数:79，代码来源:b2MotorJoint.cpp


示例7: qA

void b2WheelJoint::InitVelocityConstraints(const b2SolverData& data)
{
        m_indexA = m_bodyA->m_islandIndex;
        m_indexB = m_bodyB->m_islandIndex;
        m_localCenterA = m_bodyA->m_sweep.localCenter;
        m_localCenterB = 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;

        float32 mA = m_invMassA, mB = m_invMassB;
        float32 iA = m_invIA, iB = m_invIB;

        b2Vec2 cA = data.positions[m_indexA].c;
        float32 aA = data.positions[m_indexA].a;
        b2Vec2 vA = data.velocities[m_indexA].v;
        float32 wA = data.velocities[m_indexA].w;

        b2Vec2 cB = data.positions[m_indexB].c;
        float32 aB = data.positions[m_indexB].a;
        b2Vec2 vB = data.velocities[m_indexB].v;
        float32 wB = data.velocities[m_indexB].w;

        b2Rot qA(aA), qB(aB);

        // Compute the effective masses.
        b2Vec2 rA = b2Mul(qA, m_localAnchorA - m_localCenterA);
        b2Vec2 rB = b2Mul(qB, m_localAnchorB - m_localCenterB);
        b2Vec2 d = cB + rB - cA - rA;

        // Point to line constraint
        {
                m_ay = b2Mul(qA, m_localYAxisA);
                m_sAy = b2Cross(d + rA, m_ay);
                m_sBy = b2Cross(rB, m_ay);

                m_mass = mA + mB + iA * m_sAy * m_sAy + iB * m_sBy * m_sBy;

                if (m_mass > 0.0f)
                {
                        m_mass = 1.0f / m_mass;
                }
        }

        // Spring constraint
        m_springMass = 0.0f;
        m_bias = 0.0f;
        m_gamma = 0.0f;
        if (m_frequencyHz > 0.0f)
        {
                m_ax = b2Mul(qA, m_localXAxisA);
                m_sAx = b2Cross(d + rA, m_ax);
                m_sBx = b2Cross(rB, m_ax);

                float32 invMass = mA + mB + iA * m_sAx * m_sAx + iB * m_sBx * m_sBx;

                if (invMass > 0.0f)
                {
                        m_springMass = 1.0f / invMass;

                        float32 C = b2Dot(d, m_ax);

                        // Frequency
                        float32 omega = 2.0f * b2_pi * m_frequencyHz;

                        // Damping coefficient
                        float32 d = 2.0f * m_springMass * m_dampingRatio * omega;

                        // Spring stiffness
                        float32 k = m_springMass * omega * omega;

                        // magic formulas
                        float32 h = data.step.dt;
                        m_gamma = h * (d + h * k);
                        if (m_gamma > 0.0f)
                        {
                                m_gamma = 1.0f / m_gamma;
                        }

                        m_bias = C * h * k * m_gamma;

                        m_springMass = invMass + m_gamma;
                        if (m_springMass > 0.0f)
                        {
                                m_springMass = 1.0f / m_springMass;
                        }
                }
        }
        else
        {
                m_springImpulse = 0.0f;
        }

        // Rotational motor
        if (m_enableMotor)
        {
                m_motorMass = iA + iB;
                if (m_motorMass > 0.0f)
                {
//.........这里部分代码省略.........
开发者ID:jihyunlee，项目名称:Flying-Penguin，代码行数:101，代码来源:b2WheelJoint.cpp


示例8: qA

void b2PulleyJoint::InitVelocityConstraints(const b2SolverData& data)
{
    m_indexA = m_bodyA->m_islandIndex;
    m_indexB = m_bodyB->m_islandIndex;
    m_localCenterA = m_bodyA->m_sweep.localCenter;
    m_localCenterB = 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;

    b2Vec2 cA = data.positions[m_indexA].c;
    float32 aA = data.positions[m_indexA].a;
    b2Vec2 vA = data.velocities[m_indexA].v;
    float32 wA = data.velocities[m_indexA].w;

    b2Vec2 cB = data.positions[m_indexB].c;
    float32 aB = data.positions[m_indexB].a;
    b2Vec2 vB = data.velocities[m_indexB].v;
    float32 wB = data.velocities[m_indexB].w;

    b2Rot qA(aA), qB(aB);

    m_rA = b2Mul(qA, m_localAnchorA - m_localCenterA);
    m_rB = b2Mul(qB, m_localAnchorB - m_localCenterB);

    // Get the pulley axes.
    m_uA = cA + m_rA - m_groundAnchorA;
    m_uB = cB + m_rB - m_groundAnchorB;

    float32 lengthA = m_uA.Length();
    float32 lengthB = m_uB.Length();

    if (lengthA > 10.0f * b2_linearSlop)
    {
        m_uA *= 1.0f / lengthA;
    }
    else
    {
        m_uA.SetZero();
    }

    if (lengthB > 10.0f * b2_linearSlop)
    {
        m_uB *= 1.0f / lengthB;
    }
    else
    {
        m_uB.SetZero();
    }

    // Compute effective mass.
    float32 ruA = b2Cross(m_rA, m_uA);
    float32 ruB = b2Cross(m_rB, m_uB);

    float32 mA = m_invMassA + m_invIA * ruA * ruA;
    float32 mB = m_invMassB + m_invIB * ruB * ruB;

    m_mass = mA + m_ratio * m_ratio * mB;

    if (m_mass > 0.0f)
    {
        m_mass = 1.0f / m_mass;
    }

    if (data.step.warmStarting)
    {
        // Scale impulses to support variable time steps.
        m_impulse *= data.step.dtRatio;

        // Warm starting.
        b2Vec2 PA = -(m_impulse) * m_uA;
        b2Vec2 PB = (-m_ratio * m_impulse) * m_uB;

        vA += m_invMassA * PA;
        wA += m_invIA * b2Cross(m_rA, PA);
        vB += m_invMassB * PB;
        wB += m_invIB * b2Cross(m_rB, PB);
    }
    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;
}
开发者ID:TukekeSoft，项目名称:jacos2d-x，代码行数:89，代码来源:b2PulleyJoint.cpp


示例9: qA

void b2RevoluteJoint::InitVelocityConstraints(const b2SolverData& data)
{
    m_indexA = m_bodyA->m_islandIndex;
    m_indexB = m_bodyB->m_islandIndex;
    m_localCenterA = m_bodyA->m_sweep.localCenter;
    m_localCenterB = 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;

    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;

    b2Rot qA(aA), qB(aB);

    m_rA = b2Mul(qA, m_localAnchorA - m_localCenterA);
    m_rB = b2Mul(qB, m_localAnchorB - m_localCenterB);

    // 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]

    float32 mA = m_invMassA, mB = m_invMassB;
    float32 iA = m_invIA, iB = m_invIB;

    bool fixedRotation = (iA + iB == 0.0f);

    m_mass.ex.x = mA + mB + m_rA.y * m_rA.y * iA + m_rB.y * m_rB.y * iB;
    m_mass.ey.x = -m_rA.y * m_rA.x * iA - m_rB.y * m_rB.x * iB;
    m_mass.ez.x = -m_rA.y * iA - m_rB.y * iB;
    m_mass.ex.y = m_mass.ey.x;
    m_mass.ey.y = mA + mB + m_rA.x * m_rA.x * iA + m_rB.x * m_rB.x * iB;
    m_mass.ez.y = m_rA.x * iA + m_rB.x * iB;
    m_mass.ex.z = m_mass.ez.x;
    m_mass.ey.z = m_mass.ez.y;
    m_mass.ez.z = iA + iB;

    m_motorMass = iA + iB;
    if (m_motorMass > 0.0f)
    {
        m_motorMass = 1.0f / m_motorMass;
    }

    if (m_enableMotor == false || fixedRotation)
    {
        m_motorImpulse = 0.0f;
    }

    if (m_enableLimit && fixedRotation == false)
    {
        float32 jointAngle = aB - aA - m_referenceAngle;
        if (b2Abs(m_upperAngle - m_lowerAngle) < 2.0f * b2_angularSlop)
        {
            m_limitState = e_equalLimits;
        }
        else if (jointAngle <= m_lowerAngle)
        {
            if (m_limitState != e_atLowerLimit)
            {
                m_impulse.z = 0.0f;
            }
            m_limitState = e_atLowerLimit;
        }
        else if (jointAngle >= m_upperAngle)
        {
            if (m_limitState != e_atUpperLimit)
            {
                m_impulse.z = 0.0f;
            }
            m_limitState = e_atUpperLimit;
        }
        else
        {
            m_limitState = e_inactiveLimit;
            m_impulse.z = 0.0f;
        }
    }
    else
    {
        m_limitState = e_inactiveLimit;
    }

    if (data.step.warmStarting)
    {
        // Scale impulses to support a variable time step.
        m_impulse *= data.step.dtRatio;
        m_motorImpulse *= data.step.dtRatio;

        b2Vec2 P(m_impulse.x, m_impulse.y);
//.........这里部分代码省略.........
开发者ID:DeniLi，项目名称:Missile-Demo，代码行数:101，代码来源:b2RevoluteJoint.cpp


示例10: qB

void b2MouseJoint::InitVelocityConstraints(const b2SolverData& data)
{
	m_indexB = m_bodyB->m_islandIndex;
	m_localCenterB = m_bodyB->m_sweep.localCenter;
	m_invMassB = m_bodyB->m_invMass;
	m_invIB = m_bodyB->m_invI;

	b2Vec2 cB = data.positions[m_indexB].c;
	float32 aB = data.positions[m_indexB].a;
	b2Vec2 vB = data.velocities[m_indexB].v;
	float32 wB = data.velocities[m_indexB].w;

	b2Rot qB(aB);

	float32 mass = m_bodyB->GetMass();

	// Frequency
	float32 omega = 2.0f * b2_pi * m_frequencyHz;

	// Damping coefficient
	float32 d = 2.0f * mass * m_dampingRatio * omega;

	// Spring stiffness
	float32 k = mass * (omega * omega);

	// magic formulas
	// gamma has units of inverse mass.
	// beta has units of inverse time.
	float32 h = data.step.dt;
	b2Assert(d + h * k > b2_epsilon);
	m_gamma = h * (d + h * k);
	if (m_gamma != 0.0f)
	{
		m_gamma = 1.0f / m_gamma;
	}
	m_beta = h * k * m_gamma;

	// Compute the effective mass matrix.
	m_rB = b2Mul(qB, m_localAnchorB - m_localCenterB);

	// K    = [(1/m1 + 1/m2) * eye(2) - skew(r1) * invI1 * skew(r1) - skew(r2) * invI2 * skew(r2)]
	//      = [1/m1+1/m2     0    ] + invI1 * [r1.y*r1.y -r1.x*r1.y] + invI2 * [r1.y*r1.y -r1.x*r1.y]
	//        [    0     1/m1+1/m2]           [-r1.x*r1.y r1.x*r1.x]           [-r1.x*r1.y r1.x*r1.x]
	b2Mat22 K;
	K.ex.x = m_invMassB + m_invIB * m_rB.y * m_rB.y + m_gamma;
	K.ex.y = -m_invIB * m_rB.x * m_rB.y;
	K.ey.x = K.ex.y;
	K.ey.y = m_invMassB + m_invIB * m_rB.x * m_rB.x + m_gamma;

	m_mass = K.GetInverse();

	m_C = cB + m_rB - m_targetA;
	m_C *= m_beta;

	// Cheat with some damping
	wB *= 0.98f;

	if (data.step.warmStarting)
	{
		m_impulse *= data.step.dtRatio;
		vB += m_invMassB * m_impulse;
		wB += m_invIB * b2Cross(m_rB, m_impulse);
	}
	else
	{
		m_impulse.SetZero();
	}

	data.velocities[m_indexB].v = vB;
	data.velocities[m_indexB].w = wB;
}
开发者ID:flyover，项目名称:Box2D，代码行数:71，代码来源:b2MouseJoint.cpp



注：本文中的qB函数示例由纯净天空整理自Github/MSDocs等源码及文档管理平台，相关代码片段筛选自各路编程大神贡献的开源项目，源码版权归原作者所有，传播和使用请参考对应项目的License；未经允许，请勿转载。

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