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[sharedmemory] Fill-out calculateJacobian command.

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The server command processor actually didn't do anything with
the local point that was passed along with the calculateJacobian
command. Added in the necessary bit of math to return the
corresponding jacobian.

Also, fixed a typo in pybullet that was returning the same
jacobian for translation and rotation.
This commit is contained in:
Jeffrey Bingham
2017-09-24 14:14:24 -07:00
parent 8eb69552d1
commit ee30ca93c5
4 changed files with 47 additions and 2 deletions
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23
examples/SharedMemory/PhysicsServerCommandProcessor.cpp
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@@ -6639,9 +6639,32 @@ bool PhysicsServerCommandProcessor::processCommand(const struct SharedMemoryComm
tree->calculateJacobians(q);
btInverseDynamics::mat3x jac_t(3, numDofs + baseDofs);
btInverseDynamics::mat3x jac_r(3, numDofs + baseDofs);
// Note that inverse dynamics uses zero-based indexing of bodies, not starting from -1 for the base link.
tree->getBodyJacobianTrans(clientCmd.m_calculateJacobianArguments.m_linkIndex + 1, &jac_t);
tree->getBodyJacobianRot(clientCmd.m_calculateJacobianArguments.m_linkIndex + 1, &jac_r);
// Update the translational jacobian based on the desired local point.
// v_pt = v_frame + w x pt
// v_pt = J_t * qd + (J_r * qd) x pt
// v_pt = J_t * qd - pt x (J_r * qd)
// v_pt = J_t * qd - pt_x * J_r * qd)
// v_pt = (J_t - pt_x * J_r) * qd
// J_t_new = J_t - pt_x * J_r
btInverseDynamics::vec3 localPosition;
for (int i = 0; i < 3; ++i) {
localPosition(i) = clientCmd.m_calculateJacobianArguments.m_localPosition[i];
}
// Only calculate if the localPosition is non-zero.
if (btInverseDynamics::maxAbs(localPosition) > 0.0) {
btInverseDynamics::mat33 skewCrossProduct;
btInverseDynamics::skew(localPosition, &skewCrossProduct);
btInverseDynamics::mat3x jac_l(3, numDofs + baseDofs);
btInverseDynamics::mul(skewCrossProduct, jac_r, &jac_l);
btInverseDynamics::mat3x jac_t_new(3, numDofs + baseDofs);
btInverseDynamics::sub(jac_t, jac_l, &jac_t_new);
jac_t = jac_t_new;
}
// Fill in the result into the shared memory.
for (int i = 0; i < 3; ++i)
{
for (int j = 0; j < (numDofs + baseDofs); ++j)