anki-3d-engine/ThirdParty/Bullet/Extras/InverseDynamics/btMultiBodyTreeCreator.cpp

#include "btMultiBodyTreeCreator.hpp"

namespace btInverseDynamics
{
btMultiBodyTreeCreator::btMultiBodyTreeCreator() : m_initialized(false) {}

int btMultiBodyTreeCreator::createFromBtMultiBody(const btMultiBody *btmb, const bool verbose)
{
	if (0x0 == btmb)
	{
		bt_id_error_message("cannot create MultiBodyTree from null pointer\n");
		return -1;
	}

	// in case this is a second call, discard old data
	m_data.clear();
	m_initialized = false;

	// btMultiBody treats base link separately
	m_data.resize(1 + btmb->getNumLinks());

	// add base link data
	{
		LinkData &link = m_data[0];

		link.parent_index = -1;
		if (btmb->hasFixedBase())
		{
			link.joint_type = FIXED;
		}
		else
		{
			link.joint_type = FLOATING;
		}
		btTransform transform = (btmb->getBaseWorldTransform());
		//compute inverse dynamics in body-fixed frame
		transform.setIdentity();

		link.parent_r_parent_body_ref(0) = transform.getOrigin()[0];
		link.parent_r_parent_body_ref(1) = transform.getOrigin()[1];
		link.parent_r_parent_body_ref(2) = transform.getOrigin()[2];

		link.body_T_parent_ref(0, 0) = transform.getBasis()[0][0];
		link.body_T_parent_ref(0, 1) = transform.getBasis()[0][1];
		link.body_T_parent_ref(0, 2) = transform.getBasis()[0][2];

		link.body_T_parent_ref(1, 0) = transform.getBasis()[1][0];
		link.body_T_parent_ref(1, 1) = transform.getBasis()[1][1];
		link.body_T_parent_ref(1, 2) = transform.getBasis()[1][2];

		link.body_T_parent_ref(2, 0) = transform.getBasis()[2][0];
		link.body_T_parent_ref(2, 1) = transform.getBasis()[2][1];
		link.body_T_parent_ref(2, 2) = transform.getBasis()[2][2];

		// random unit vector. value not used for fixed or floating joints.
		link.body_axis_of_motion(0) = 0;
		link.body_axis_of_motion(1) = 0;
		link.body_axis_of_motion(2) = 1;

		link.mass = btmb->getBaseMass();
		// link frame in the center of mass
		link.body_r_body_com(0) = 0;
		link.body_r_body_com(1) = 0;
		link.body_r_body_com(2) = 0;
		// BulletDynamics uses body-fixed frame in the cog, aligned with principal axes
		link.body_I_body(0, 0) = btmb->getBaseInertia()[0];
		link.body_I_body(0, 1) = 0.0;
		link.body_I_body(0, 2) = 0.0;
		link.body_I_body(1, 0) = 0.0;
		link.body_I_body(1, 1) = btmb->getBaseInertia()[1];
		link.body_I_body(1, 2) = 0.0;
		link.body_I_body(2, 0) = 0.0;
		link.body_I_body(2, 1) = 0.0;
		link.body_I_body(2, 2) = btmb->getBaseInertia()[2];
		// shift reference point to link origin (in joint axis)
		mat33 tilde_r_com = tildeOperator(link.body_r_body_com);
		link.body_I_body = link.body_I_body - link.mass * tilde_r_com * tilde_r_com;
		if (verbose)
		{
			id_printf(
				"base: mass= %f, bt_inertia= [%f %f %f]\n"
				"Io= [%f %f %f;\n"
				"    %f %f %f;\n"
				"    %f %f %f]\n",
				link.mass, btmb->getBaseInertia()[0], btmb->getBaseInertia()[1],
				btmb->getBaseInertia()[2], link.body_I_body(0, 0), link.body_I_body(0, 1),
				link.body_I_body(0, 2), link.body_I_body(1, 0), link.body_I_body(1, 1),
				link.body_I_body(1, 2), link.body_I_body(2, 0), link.body_I_body(2, 1),
				link.body_I_body(2, 2));
		}
	}

	for (int bt_index = 0; bt_index < btmb->getNumLinks(); bt_index++)
	{
		if (verbose)
		{
			id_printf("bt->id: converting link %d\n", bt_index);
		}
		const btMultibodyLink &bt_link = btmb->getLink(bt_index);
		LinkData &link = m_data[bt_index + 1];

		link.parent_index = bt_link.m_parent + 1;

		link.mass = bt_link.m_mass;
		if (verbose)
		{
			id_printf("mass= %f\n", link.mass);
		}
		// from this body's pivot to this body's com in this body's frame
		link.body_r_body_com[0] = bt_link.m_dVector[0];
		link.body_r_body_com[1] = bt_link.m_dVector[1];
		link.body_r_body_com[2] = bt_link.m_dVector[2];
		if (verbose)
		{
			id_printf("com= %f %f %f\n", link.body_r_body_com[0], link.body_r_body_com[1],
					  link.body_r_body_com[2]);
		}
		// BulletDynamics uses a body-fixed frame in the CoM, aligned with principal axes
		link.body_I_body(0, 0) = bt_link.m_inertiaLocal[0];
		link.body_I_body(0, 1) = 0.0;
		link.body_I_body(0, 2) = 0.0;
		link.body_I_body(1, 0) = 0.0;
		link.body_I_body(1, 1) = bt_link.m_inertiaLocal[1];
		link.body_I_body(1, 2) = 0.0;
		link.body_I_body(2, 0) = 0.0;
		link.body_I_body(2, 1) = 0.0;
		link.body_I_body(2, 2) = bt_link.m_inertiaLocal[2];
		// shift reference point to link origin (in joint axis)
		mat33 tilde_r_com = tildeOperator(link.body_r_body_com);
		link.body_I_body = link.body_I_body - link.mass * tilde_r_com * tilde_r_com;

		if (verbose)
		{
			id_printf(
				"link %d: mass= %f, bt_inertia= [%f %f %f]\n"
				"Io= [%f %f %f;\n"
				"    %f %f %f;\n"
				"    %f %f %f]\n",
				bt_index, link.mass, bt_link.m_inertiaLocal[0], bt_link.m_inertiaLocal[1],
				bt_link.m_inertiaLocal[2], link.body_I_body(0, 0), link.body_I_body(0, 1),
				link.body_I_body(0, 2), link.body_I_body(1, 0), link.body_I_body(1, 1),
				link.body_I_body(1, 2), link.body_I_body(2, 0), link.body_I_body(2, 1),
				link.body_I_body(2, 2));
		}
		// transform for vectors written in parent frame to this link's body-fixed frame
		btMatrix3x3 basis = btTransform(bt_link.m_zeroRotParentToThis).getBasis();
		link.body_T_parent_ref(0, 0) = basis[0][0];
		link.body_T_parent_ref(0, 1) = basis[0][1];
		link.body_T_parent_ref(0, 2) = basis[0][2];
		link.body_T_parent_ref(1, 0) = basis[1][0];
		link.body_T_parent_ref(1, 1) = basis[1][1];
		link.body_T_parent_ref(1, 2) = basis[1][2];
		link.body_T_parent_ref(2, 0) = basis[2][0];
		link.body_T_parent_ref(2, 1) = basis[2][1];
		link.body_T_parent_ref(2, 2) = basis[2][2];
		if (verbose)
		{
			id_printf(
				"body_T_parent_ref= %f %f %f\n"
				"                   %f %f %f\n"
				"                   %f %f %f\n",
				basis[0][0], basis[0][1], basis[0][2], basis[1][0], basis[1][1], basis[1][2],
				basis[2][0], basis[2][1], basis[2][2]);
		}
		switch (bt_link.m_jointType)
		{
			case btMultibodyLink::eRevolute:
				link.joint_type = REVOLUTE;
				if (verbose)
				{
					id_printf("type= revolute\n");
				}
				link.body_axis_of_motion(0) = bt_link.m_axes[0].m_topVec[0];
				link.body_axis_of_motion(1) = bt_link.m_axes[0].m_topVec[1];
				link.body_axis_of_motion(2) = bt_link.m_axes[0].m_topVec[2];

				// for revolute joints, m_eVector = parentComToThisPivotOffset
				//                      m_dVector = thisPivotToThisComOffset
				// from parent com to pivot, in parent frame
				link.parent_r_parent_body_ref(0) = bt_link.m_eVector[0];
				link.parent_r_parent_body_ref(1) = bt_link.m_eVector[1];
				link.parent_r_parent_body_ref(2) = bt_link.m_eVector[2];
				break;
			case btMultibodyLink::ePrismatic:
				link.joint_type = PRISMATIC;
				if (verbose)
				{
					id_printf("type= prismatic\n");
				}
				link.body_axis_of_motion(0) = bt_link.m_axes[0].m_bottomVec[0];
				link.body_axis_of_motion(1) = bt_link.m_axes[0].m_bottomVec[1];
				link.body_axis_of_motion(2) = bt_link.m_axes[0].m_bottomVec[2];

				// for prismatic joints, eVector
				//                                according to documentation :
				//                                parentComToThisComOffset
				//                                but seems to be: from parent's com to parent's
				//                                pivot ??
				//                       m_dVector = thisPivotToThisComOffset
				link.parent_r_parent_body_ref(0) = bt_link.m_eVector[0];
				link.parent_r_parent_body_ref(1) = bt_link.m_eVector[1];
				link.parent_r_parent_body_ref(2) = bt_link.m_eVector[2];
				break;
			case btMultibodyLink::eSpherical:
				link.joint_type = SPHERICAL;
				link.parent_r_parent_body_ref(0) = bt_link.m_eVector[0];
				link.parent_r_parent_body_ref(1) = bt_link.m_eVector[1];
				link.parent_r_parent_body_ref(2) = bt_link.m_eVector[2];
				// random unit vector
				link.body_axis_of_motion(0) = 0;
				link.body_axis_of_motion(1) = 1;
				link.body_axis_of_motion(2) = 0;
				break;
			case btMultibodyLink::ePlanar:
				bt_id_error_message("planar joints not implemented\n");
				return -1;
			case btMultibodyLink::eFixed:
				link.joint_type = FIXED;
				// random unit vector
				link.body_axis_of_motion(0) = 0;
				link.body_axis_of_motion(1) = 0;
				link.body_axis_of_motion(2) = 1;

				// for fixed joints, m_dVector = thisPivotToThisComOffset;
				//                   m_eVector = parentComToThisPivotOffset;
				link.parent_r_parent_body_ref(0) = bt_link.m_eVector[0];
				link.parent_r_parent_body_ref(1) = bt_link.m_eVector[1];
				link.parent_r_parent_body_ref(2) = bt_link.m_eVector[2];
				break;
			default:
				bt_id_error_message("unknown btMultiBody::eFeatherstoneJointType %d\n",
									bt_link.m_jointType);
				return -1;
		}
		if (link.parent_index > 0)
		{  // parent body isn't the root
			const btMultibodyLink &bt_parent_link = btmb->getLink(link.parent_index - 1);
			// from parent pivot to parent com, in parent frame
			link.parent_r_parent_body_ref(0) += bt_parent_link.m_dVector[0];
			link.parent_r_parent_body_ref(1) += bt_parent_link.m_dVector[1];
			link.parent_r_parent_body_ref(2) += bt_parent_link.m_dVector[2];
		}
		else
		{
			// parent is root body. btMultiBody only knows 6-DoF or 0-DoF root bodies,
			// whose link frame is in the CoM (ie, no notion of a pivot point)
		}

		if (verbose)
		{
			id_printf("parent_r_parent_body_ref= %f %f %f\n", link.parent_r_parent_body_ref[0],
					  link.parent_r_parent_body_ref[1], link.parent_r_parent_body_ref[2]);
		}
	}

	m_initialized = true;

	return 0;
}

int btMultiBodyTreeCreator::getNumBodies(int *num_bodies) const
{
	if (false == m_initialized)
	{
		bt_id_error_message("btMultiBody not converted yet\n");
		return -1;
	}

	*num_bodies = static_cast<int>(m_data.size());
	return 0;
}

int btMultiBodyTreeCreator::getBody(const int body_index, int *parent_index, JointType *joint_type,
									vec3 *parent_r_parent_body_ref, mat33 *body_T_parent_ref,
									vec3 *body_axis_of_motion, idScalar *mass,
									vec3 *body_r_body_com, mat33 *body_I_body, int *user_int,
									void **user_ptr) const
{
	if (false == m_initialized)
	{
		bt_id_error_message("MultiBodyTree not created yet\n");
		return -1;
	}

	if (body_index < 0 || body_index >= static_cast<int>(m_data.size()))
	{
		bt_id_error_message("index out of range (got %d but only %zu bodies)\n", body_index,
							m_data.size());
		return -1;
	}

	*parent_index = m_data[body_index].parent_index;
	*joint_type = m_data[body_index].joint_type;
	*parent_r_parent_body_ref = m_data[body_index].parent_r_parent_body_ref;
	*body_T_parent_ref = m_data[body_index].body_T_parent_ref;
	*body_axis_of_motion = m_data[body_index].body_axis_of_motion;
	*mass = m_data[body_index].mass;
	*body_r_body_com = m_data[body_index].body_r_body_com;
	*body_I_body = m_data[body_index].body_I_body;

	*user_int = -1;
	*user_ptr = 0x0;

	return 0;
}
}  // namespace btInverseDynamics