void btHingeConstraint::getInfo1(btConstraintInfo1* info)
{
if (m_useSolveConstraintObsolete)
{
info->m_numConstraintRows = 0;
info->nub = 0;
}
else
{
info->m_numConstraintRows = 5; // Fixed 3 linear + 2 angular
info->nub = 1;
//prepare constraint
testLimit();
if(getSolveLimit() || getEnableAngularMotor())
{
info->m_numConstraintRows++; // limit 3rd anguar as well
info->nub--;
}
}
}
void btHingeConstraint::getInfo1(btConstraintInfo1* info)
{
if (m_useSolveConstraintObsolete)
{
info->m_numConstraintRows = 0;
info->nub = 0;
}
else
{
info->m_numConstraintRows = 5; // Fixed 3 linear + 2 angular
info->nub = 1;
//always add the row, to avoid computation (data is not available yet)
//prepare constraint
testLimit(m_rbA.getCenterOfMassTransform(),m_rbB.getCenterOfMassTransform());
if(getSolveLimit() || getEnableAngularMotor())
{
info->m_numConstraintRows++; // limit 3rd anguar as well
info->nub--;
}
}
}
void btHingeConstraint::getInfo2InternalUsingFrameOffset(btConstraintInfo2* info, const btTransform& transA,const btTransform& transB,const btVector3& angVelA,const btVector3& angVelB)
{
btAssert(!m_useSolveConstraintObsolete);
int i, s = info->rowskip;
// transforms in world space
btTransform trA = transA*m_rbAFrame;
btTransform trB = transB*m_rbBFrame;
// pivot point
btVector3 pivotAInW = trA.getOrigin();
btVector3 pivotBInW = trB.getOrigin();
#if 1
// difference between frames in WCS
btVector3 ofs = trB.getOrigin() - trA.getOrigin();
// now get weight factors depending on masses
btScalar miA = getRigidBodyA().getInvMass();
btScalar miB = getRigidBodyB().getInvMass();
bool hasStaticBody = (miA < SIMD_EPSILON) || (miB < SIMD_EPSILON);
btScalar miS = miA + miB;
btScalar factA, factB;
if(miS > btScalar(0.f))
{
factA = miB / miS;
}
else
{
factA = btScalar(0.5f);
}
factB = btScalar(1.0f) - factA;
// get the desired direction of hinge axis
// as weighted sum of Z-orthos of frameA and frameB in WCS
btVector3 ax1A = trA.getBasis().getColumn(2);
btVector3 ax1B = trB.getBasis().getColumn(2);
btVector3 ax1 = ax1A * factA + ax1B * factB;
ax1.normalize();
// fill first 3 rows
// we want: velA + wA x relA == velB + wB x relB
btTransform bodyA_trans = transA;
btTransform bodyB_trans = transB;
int s0 = 0;
int s1 = s;
int s2 = s * 2;
int nrow = 2; // last filled row
btVector3 tmpA, tmpB, relA, relB, p, q;
// get vector from bodyB to frameB in WCS
relB = trB.getOrigin() - bodyB_trans.getOrigin();
// get its projection to hinge axis
btVector3 projB = ax1 * relB.dot(ax1);
// get vector directed from bodyB to hinge axis (and orthogonal to it)
btVector3 orthoB = relB - projB;
// same for bodyA
relA = trA.getOrigin() - bodyA_trans.getOrigin();
btVector3 projA = ax1 * relA.dot(ax1);
btVector3 orthoA = relA - projA;
btVector3 totalDist = projA - projB;
// get offset vectors relA and relB
relA = orthoA + totalDist * factA;
relB = orthoB - totalDist * factB;
// now choose average ortho to hinge axis
p = orthoB * factA + orthoA * factB;
btScalar len2 = p.length2();
if(len2 > SIMD_EPSILON)
{
p /= btSqrt(len2);
}
else
{
p = trA.getBasis().getColumn(1);
}
// make one more ortho
q = ax1.cross(p);
// fill three rows
tmpA = relA.cross(p);
tmpB = relB.cross(p);
for (i=0; i<3; i++) info->m_J1angularAxis[s0+i] = tmpA[i];
for (i=0; i<3; i++) info->m_J2angularAxis[s0+i] = -tmpB[i];
tmpA = relA.cross(q);
tmpB = relB.cross(q);
if(hasStaticBody && getSolveLimit())
{ // to make constraint between static and dynamic objects more rigid
// remove wA (or wB) from equation if angular limit is hit
tmpB *= factB;
tmpA *= factA;
}
for (i=0; i<3; i++) info->m_J1angularAxis[s1+i] = tmpA[i];
for (i=0; i<3; i++) info->m_J2angularAxis[s1+i] = -tmpB[i];
tmpA = relA.cross(ax1);
tmpB = relB.cross(ax1);
if(hasStaticBody)
{ // to make constraint between static and dynamic objects more rigid
// remove wA (or wB) from equation
tmpB *= factB;
tmpA *= factA;
}
for (i=0; i<3; i++) info->m_J1angularAxis[s2+i] = tmpA[i];
for (i=0; i<3; i++) info->m_J2angularAxis[s2+i] = -tmpB[i];
for (i=0; i<3; i++) info->m_J1linearAxis[s0+i] = p[i];
for (i=0; i<3; i++) info->m_J1linearAxis[s1+i] = q[i];
for (i=0; i<3; i++) info->m_J1linearAxis[s2+i] = ax1[i];
// compute three elements of right hand side
btScalar k = info->fps * info->erp;
btScalar rhs = k * p.dot(ofs);
info->m_constraintError[s0] = rhs;
rhs = k * q.dot(ofs);
info->m_constraintError[s1] = rhs;
rhs = k * ax1.dot(ofs);
info->m_constraintError[s2] = rhs;
// the hinge axis should be the only unconstrained
// rotational axis, the angular velocity of the two bodies perpendicular to
// the hinge axis should be equal. thus the constraint equations are
// p*w1 - p*w2 = 0
// q*w1 - q*w2 = 0
// where p and q are unit vectors normal to the hinge axis, and w1 and w2
// are the angular velocity vectors of the two bodies.
int s3 = 3 * s;
int s4 = 4 * s;
info->m_J1angularAxis[s3 + 0] = p[0];
info->m_J1angularAxis[s3 + 1] = p[1];
info->m_J1angularAxis[s3 + 2] = p[2];
info->m_J1angularAxis[s4 + 0] = q[0];
info->m_J1angularAxis[s4 + 1] = q[1];
info->m_J1angularAxis[s4 + 2] = q[2];
info->m_J2angularAxis[s3 + 0] = -p[0];
info->m_J2angularAxis[s3 + 1] = -p[1];
info->m_J2angularAxis[s3 + 2] = -p[2];
info->m_J2angularAxis[s4 + 0] = -q[0];
info->m_J2angularAxis[s4 + 1] = -q[1];
info->m_J2angularAxis[s4 + 2] = -q[2];
// compute the right hand side of the constraint equation. set relative
// body velocities along p and q to bring the hinge back into alignment.
// if ax1A,ax1B are the unit length hinge axes as computed from bodyA and
// bodyB, we need to rotate both bodies along the axis u = (ax1 x ax2).
// if "theta" is the angle between ax1 and ax2, we need an angular velocity
// along u to cover angle erp*theta in one step :
// |angular_velocity| = angle/time = erp*theta / stepsize
// = (erp*fps) * theta
// angular_velocity = |angular_velocity| * (ax1 x ax2) / |ax1 x ax2|
// = (erp*fps) * theta * (ax1 x ax2) / sin(theta)
// ...as ax1 and ax2 are unit length. if theta is smallish,
// theta ~= sin(theta), so
// angular_velocity = (erp*fps) * (ax1 x ax2)
// ax1 x ax2 is in the plane space of ax1, so we project the angular
// velocity to p and q to find the right hand side.
k = info->fps * info->erp;
btVector3 u = ax1A.cross(ax1B);
info->m_constraintError[s3] = k * u.dot(p);
info->m_constraintError[s4] = k * u.dot(q);
#endif
// check angular limits
nrow = 4; // last filled row
int srow;
btScalar limit_err = btScalar(0.0);
int limit = 0;
if(getSolveLimit())
{
limit_err = m_correction * m_referenceSign;
limit = (limit_err > btScalar(0.0)) ? 1 : 2;
}
// if the hinge has joint limits or motor, add in the extra row
int powered = 0;
if(getEnableAngularMotor())
{
powered = 1;
}
if(limit || powered)
{
nrow++;
srow = nrow * info->rowskip;
info->m_J1angularAxis[srow+0] = ax1[0];
info->m_J1angularAxis[srow+1] = ax1[1];
info->m_J1angularAxis[srow+2] = ax1[2];
info->m_J2angularAxis[srow+0] = -ax1[0];
info->m_J2angularAxis[srow+1] = -ax1[1];
info->m_J2angularAxis[srow+2] = -ax1[2];
btScalar lostop = getLowerLimit();
btScalar histop = getUpperLimit();
if(limit && (lostop == histop))
{ // the joint motor is ineffective
powered = 0;
}
info->m_constraintError[srow] = btScalar(0.0f);
btScalar currERP = (m_flags & BT_HINGE_FLAGS_ERP_STOP) ? m_stopERP : info->erp;
if(powered)
{
if(m_flags & BT_HINGE_FLAGS_CFM_NORM)
{
info->cfm[srow] = m_normalCFM;
}
btScalar mot_fact = getMotorFactor(m_hingeAngle, lostop, histop, m_motorTargetVelocity, info->fps * currERP);
info->m_constraintError[srow] += mot_fact * m_motorTargetVelocity * m_referenceSign;
info->m_lowerLimit[srow] = - m_maxMotorImpulse;
info->m_upperLimit[srow] = m_maxMotorImpulse;
}
if(limit)
{
k = info->fps * currERP;
info->m_constraintError[srow] += k * limit_err;
if(m_flags & BT_HINGE_FLAGS_CFM_STOP)
{
info->cfm[srow] = m_stopCFM;
}
if(lostop == histop)
{
// limited low and high simultaneously
info->m_lowerLimit[srow] = -SIMD_INFINITY;
info->m_upperLimit[srow] = SIMD_INFINITY;
}
else if(limit == 1)
{ // low limit
info->m_lowerLimit[srow] = 0;
info->m_upperLimit[srow] = SIMD_INFINITY;
}
else
{ // high limit
info->m_lowerLimit[srow] = -SIMD_INFINITY;
info->m_upperLimit[srow] = 0;
}
// bounce (we'll use slider parameter abs(1.0 - m_dampingLimAng) for that)
btScalar bounce = m_relaxationFactor;
if(bounce > btScalar(0.0))
{
btScalar vel = angVelA.dot(ax1);
vel -= angVelB.dot(ax1);
// only apply bounce if the velocity is incoming, and if the
// resulting c[] exceeds what we already have.
if(limit == 1)
{ // low limit
if(vel < 0)
{
btScalar newc = -bounce * vel;
if(newc > info->m_constraintError[srow])
{
info->m_constraintError[srow] = newc;
}
}
}
else
{ // high limit - all those computations are reversed
if(vel > 0)
{
btScalar newc = -bounce * vel;
if(newc < info->m_constraintError[srow])
{
info->m_constraintError[srow] = newc;
}
}
}
}
info->m_constraintError[srow] *= m_biasFactor;
} // if(limit)
} // if angular limit or powered
}
void btHingeConstraint::getInfo2Internal(btConstraintInfo2* info, const btTransform& transA,const btTransform& transB,const btVector3& angVelA,const btVector3& angVelB)
{
btAssert(!m_useSolveConstraintObsolete);
int i, skip = info->rowskip;
// transforms in world space
btTransform trA = transA*m_rbAFrame;
btTransform trB = transB*m_rbBFrame;
// pivot point
btVector3 pivotAInW = trA.getOrigin();
btVector3 pivotBInW = trB.getOrigin();
#if 0
if (0)
{
for (i=0;i<6;i++)
{
info->m_J1linearAxis[i*skip]=0;
info->m_J1linearAxis[i*skip+1]=0;
info->m_J1linearAxis[i*skip+2]=0;
info->m_J1angularAxis[i*skip]=0;
info->m_J1angularAxis[i*skip+1]=0;
info->m_J1angularAxis[i*skip+2]=0;
info->m_J2angularAxis[i*skip]=0;
info->m_J2angularAxis[i*skip+1]=0;
info->m_J2angularAxis[i*skip+2]=0;
info->m_constraintError[i*skip]=0.f;
}
}
#endif //#if 0
// linear (all fixed)
info->m_J1linearAxis[0] = 1;
info->m_J1linearAxis[skip + 1] = 1;
info->m_J1linearAxis[2 * skip + 2] = 1;
btVector3 a1 = pivotAInW - transA.getOrigin();
{
btVector3* angular0 = (btVector3*)(info->m_J1angularAxis);
btVector3* angular1 = (btVector3*)(info->m_J1angularAxis + skip);
btVector3* angular2 = (btVector3*)(info->m_J1angularAxis + 2 * skip);
btVector3 a1neg = -a1;
a1neg.getSkewSymmetricMatrix(angular0,angular1,angular2);
}
btVector3 a2 = pivotBInW - transB.getOrigin();
{
btVector3* angular0 = (btVector3*)(info->m_J2angularAxis);
btVector3* angular1 = (btVector3*)(info->m_J2angularAxis + skip);
btVector3* angular2 = (btVector3*)(info->m_J2angularAxis + 2 * skip);
a2.getSkewSymmetricMatrix(angular0,angular1,angular2);
}
// linear RHS
btScalar k = info->fps * info->erp;
for(i = 0; i < 3; i++)
{
info->m_constraintError[i * skip] = k * (pivotBInW[i] - pivotAInW[i]);
}
// make rotations around X and Y equal
// the hinge axis should be the only unconstrained
// rotational axis, the angular velocity of the two bodies perpendicular to
// the hinge axis should be equal. thus the constraint equations are
// p*w1 - p*w2 = 0
// q*w1 - q*w2 = 0
// where p and q are unit vectors normal to the hinge axis, and w1 and w2
// are the angular velocity vectors of the two bodies.
// get hinge axis (Z)
btVector3 ax1 = trA.getBasis().getColumn(2);
// get 2 orthos to hinge axis (X, Y)
btVector3 p = trA.getBasis().getColumn(0);
btVector3 q = trA.getBasis().getColumn(1);
// set the two hinge angular rows
int s3 = 3 * info->rowskip;
int s4 = 4 * info->rowskip;
info->m_J1angularAxis[s3 + 0] = p[0];
info->m_J1angularAxis[s3 + 1] = p[1];
info->m_J1angularAxis[s3 + 2] = p[2];
info->m_J1angularAxis[s4 + 0] = q[0];
info->m_J1angularAxis[s4 + 1] = q[1];
info->m_J1angularAxis[s4 + 2] = q[2];
info->m_J2angularAxis[s3 + 0] = -p[0];
info->m_J2angularAxis[s3 + 1] = -p[1];
info->m_J2angularAxis[s3 + 2] = -p[2];
info->m_J2angularAxis[s4 + 0] = -q[0];
info->m_J2angularAxis[s4 + 1] = -q[1];
info->m_J2angularAxis[s4 + 2] = -q[2];
// compute the right hand side of the constraint equation. set relative
// body velocities along p and q to bring the hinge back into alignment.
// if ax1,ax2 are the unit length hinge axes as computed from body1 and
// body2, we need to rotate both bodies along the axis u = (ax1 x ax2).
// if `theta' is the angle between ax1 and ax2, we need an angular velocity
// along u to cover angle erp*theta in one step :
// |angular_velocity| = angle/time = erp*theta / stepsize
// = (erp*fps) * theta
// angular_velocity = |angular_velocity| * (ax1 x ax2) / |ax1 x ax2|
// = (erp*fps) * theta * (ax1 x ax2) / sin(theta)
// ...as ax1 and ax2 are unit length. if theta is smallish,
// theta ~= sin(theta), so
// angular_velocity = (erp*fps) * (ax1 x ax2)
// ax1 x ax2 is in the plane space of ax1, so we project the angular
// velocity to p and q to find the right hand side.
btVector3 ax2 = trB.getBasis().getColumn(2);
btVector3 u = ax1.cross(ax2);
info->m_constraintError[s3] = k * u.dot(p);
info->m_constraintError[s4] = k * u.dot(q);
// check angular limits
int nrow = 4; // last filled row
int srow;
btScalar limit_err = btScalar(0.0);
int limit = 0;
if(getSolveLimit())
{
limit_err = m_correction * m_referenceSign;
limit = (limit_err > btScalar(0.0)) ? 1 : 2;
}
// if the hinge has joint limits or motor, add in the extra row
int powered = 0;
if(getEnableAngularMotor())
{
powered = 1;
}
if(limit || powered)
{
nrow++;
srow = nrow * info->rowskip;
info->m_J1angularAxis[srow+0] = ax1[0];
info->m_J1angularAxis[srow+1] = ax1[1];
info->m_J1angularAxis[srow+2] = ax1[2];
info->m_J2angularAxis[srow+0] = -ax1[0];
info->m_J2angularAxis[srow+1] = -ax1[1];
info->m_J2angularAxis[srow+2] = -ax1[2];
btScalar lostop = getLowerLimit();
btScalar histop = getUpperLimit();
if(limit && (lostop == histop))
{ // the joint motor is ineffective
powered = 0;
}
info->m_constraintError[srow] = btScalar(0.0f);
btScalar currERP = (m_flags & BT_HINGE_FLAGS_ERP_STOP) ? m_stopERP : info->erp;
if(powered)
{
if(m_flags & BT_HINGE_FLAGS_CFM_NORM)
{
info->cfm[srow] = m_normalCFM;
}
btScalar mot_fact = getMotorFactor(m_hingeAngle, lostop, histop, m_motorTargetVelocity, info->fps * currERP);
info->m_constraintError[srow] += mot_fact * m_motorTargetVelocity * m_referenceSign;
info->m_lowerLimit[srow] = - m_maxMotorImpulse;
info->m_upperLimit[srow] = m_maxMotorImpulse;
}
if(limit)
{
k = info->fps * currERP;
info->m_constraintError[srow] += k * limit_err;
if(m_flags & BT_HINGE_FLAGS_CFM_STOP)
{
info->cfm[srow] = m_stopCFM;
}
if(lostop == histop)
{
// limited low and high simultaneously
info->m_lowerLimit[srow] = -SIMD_INFINITY;
info->m_upperLimit[srow] = SIMD_INFINITY;
}
else if(limit == 1)
{ // low limit
info->m_lowerLimit[srow] = 0;
info->m_upperLimit[srow] = SIMD_INFINITY;
}
else
{ // high limit
info->m_lowerLimit[srow] = -SIMD_INFINITY;
info->m_upperLimit[srow] = 0;
}
// bounce (we'll use slider parameter abs(1.0 - m_dampingLimAng) for that)
btScalar bounce = m_relaxationFactor;
if(bounce > btScalar(0.0))
{
btScalar vel = angVelA.dot(ax1);
vel -= angVelB.dot(ax1);
// only apply bounce if the velocity is incoming, and if the
// resulting c[] exceeds what we already have.
if(limit == 1)
{ // low limit
if(vel < 0)
{
btScalar newc = -bounce * vel;
if(newc > info->m_constraintError[srow])
{
info->m_constraintError[srow] = newc;
}
}
}
else
{ // high limit - all those computations are reversed
if(vel > 0)
{
btScalar newc = -bounce * vel;
if(newc < info->m_constraintError[srow])
{
info->m_constraintError[srow] = newc;
}
}
}
}
info->m_constraintError[srow] *= m_biasFactor;
} // if(limit)
} // if angular limit or powered
}