Remove unused Bullet module and thirdparty code

It has been disabled in `master` since one year (#45852) and our plan
is for Bullet, and possibly other thirdparty physics engines, to be
implemented via GDExtension so that they can be selected by the users
who need them.

1 files changed, 0 insertions, 1286 deletions

diff --git a/thirdparty/bullet/BulletInverseDynamics/details/MultiBodyTreeImpl.cpp b/thirdparty/bullet/BulletInverseDynamics/details/MultiBodyTreeImpl.cpp
deleted file mode 100644
index ec9a562295..0000000000
--- a/thirdparty/bullet/BulletInverseDynamics/details/MultiBodyTreeImpl.cpp
+++ /dev/null
@@ -1,1286 +0,0 @@
-#include "MultiBodyTreeImpl.hpp"
-
-namespace btInverseDynamics
-{
-MultiBodyTree::MultiBodyImpl::MultiBodyImpl(int num_bodies_, int num_dofs_)
-	: m_num_bodies(num_bodies_), m_num_dofs(num_dofs_)
-#if (defined BT_ID_HAVE_MAT3X) && (defined BT_ID_WITH_JACOBIANS)
-	  ,
-	  m_m3x(3, m_num_dofs)
-#endif
-{
-#if (defined BT_ID_HAVE_MAT3X) && (defined BT_ID_WITH_JACOBIANS)
-	resize(m_m3x, m_num_dofs);
-#endif
-	m_body_list.resize(num_bodies_);
-	m_parent_index.resize(num_bodies_);
-	m_child_indices.resize(num_bodies_);
-	m_user_int.resize(num_bodies_);
-	m_user_ptr.resize(num_bodies_);
-
-	m_world_gravity(0) = 0.0;
-	m_world_gravity(1) = 0.0;
-	m_world_gravity(2) = -9.8;
-}
-
-const char *MultiBodyTree::MultiBodyImpl::jointTypeToString(const JointType &type) const
-{
-	switch (type)
-	{
-		case FIXED:
-			return "fixed";
-		case REVOLUTE:
-			return "revolute";
-		case PRISMATIC:
-			return "prismatic";
-		case FLOATING:
-			return "floating";
-		case SPHERICAL:
-			return "spherical";
-	}
-	return "error: invalid";
-}
-
-inline void indent(const int &level)
-{
-	for (int j = 0; j < level; j++)
-		id_printf("  ");  // indent
-}
-
-void MultiBodyTree::MultiBodyImpl::printTree()
-{
-	id_printf("body %.2d[%s]: root\n", 0, jointTypeToString(m_body_list[0].m_joint_type));
-	printTree(0, 0);
-}
-
-void MultiBodyTree::MultiBodyImpl::printTreeData()
-{
-	for (idArrayIdx i = 0; i < m_body_list.size(); i++)
-	{
-		RigidBody &body = m_body_list[i];
-		id_printf("body: %d\n", static_cast<int>(i));
-		id_printf("type: %s\n", jointTypeToString(body.m_joint_type));
-		id_printf("q_index= %d\n", body.m_q_index);
-		id_printf("Jac_JR= [%f;%f;%f]\n", body.m_Jac_JR(0), body.m_Jac_JR(1), body.m_Jac_JR(2));
-		id_printf("Jac_JT= [%f;%f;%f]\n", body.m_Jac_JT(0), body.m_Jac_JT(1), body.m_Jac_JT(2));
-
-		id_printf("mass = %f\n", body.m_mass);
-		id_printf("mass * com = [%f %f %f]\n", body.m_body_mass_com(0), body.m_body_mass_com(1),
-				  body.m_body_mass_com(2));
-		id_printf(
-			"I_o= [%f %f %f;\n"
-			"	  %f %f %f;\n"
-			"	  %f %f %f]\n",
-			body.m_body_I_body(0, 0), body.m_body_I_body(0, 1), body.m_body_I_body(0, 2),
-			body.m_body_I_body(1, 0), body.m_body_I_body(1, 1), body.m_body_I_body(1, 2),
-			body.m_body_I_body(2, 0), body.m_body_I_body(2, 1), body.m_body_I_body(2, 2));
-
-		id_printf("parent_pos_parent_body_ref= [%f %f %f]\n", body.m_parent_pos_parent_body_ref(0),
-				  body.m_parent_pos_parent_body_ref(1), body.m_parent_pos_parent_body_ref(2));
-	}
-}
-int MultiBodyTree::MultiBodyImpl::bodyNumDoFs(const JointType &type) const
-{
-	switch (type)
-	{
-		case FIXED:
-			return 0;
-		case REVOLUTE:
-		case PRISMATIC:
-			return 1;
-		case FLOATING:
-			return 6;
-		case SPHERICAL:
-			return 3;
-	}
-	bt_id_error_message("unknown joint type %d\n", type);
-	return 0;
-}
-
-void MultiBodyTree::MultiBodyImpl::printTree(int index, int indentation)
-{
-	// this is adapted from URDF2Bullet.
-	// TODO: fix this and print proper graph (similar to git --log --graph)
-	int num_children = m_child_indices[index].size();
-
-	indentation += 2;
-	int count = 0;
-
-	for (int i = 0; i < num_children; i++)
-	{
-		int child_index = m_child_indices[index][i];
-		indent(indentation);
-		id_printf("body %.2d[%s]: %.2d is child no. %d (qi= %d .. %d) \n", index,
-				  jointTypeToString(m_body_list[index].m_joint_type), child_index, (count++) + 1,
-				  m_body_list[index].m_q_index,
-				  m_body_list[index].m_q_index + bodyNumDoFs(m_body_list[index].m_joint_type));
-		// first grandchild
-		printTree(child_index, indentation);
-	}
-}
-
-int MultiBodyTree::MultiBodyImpl::setGravityInWorldFrame(const vec3 &gravity)
-{
-	m_world_gravity = gravity;
-	return 0;
-}
-
-int MultiBodyTree::MultiBodyImpl::generateIndexSets()
-{
-	m_body_revolute_list.resize(0);
-	m_body_prismatic_list.resize(0);
-	int q_index = 0;
-	for (idArrayIdx i = 0; i < m_body_list.size(); i++)
-	{
-		RigidBody &body = m_body_list[i];
-		body.m_q_index = -1;
-		switch (body.m_joint_type)
-		{
-			case REVOLUTE:
-				m_body_revolute_list.push_back(i);
-				body.m_q_index = q_index;
-				q_index++;
-				break;
-			case PRISMATIC:
-				m_body_prismatic_list.push_back(i);
-				body.m_q_index = q_index;
-				q_index++;
-				break;
-			case FIXED:
-				// do nothing
-				break;
-			case FLOATING:
-				m_body_floating_list.push_back(i);
-				body.m_q_index = q_index;
-				q_index += 6;
-				break;
-			case SPHERICAL:
-				m_body_spherical_list.push_back(i);
-				body.m_q_index = q_index;
-				q_index += 3;
-				break;
-			default:
-				bt_id_error_message("unsupported joint type %d\n", body.m_joint_type);
-				return -1;
-		}
-	}
-	// sanity check
-	if (q_index != m_num_dofs)
-	{
-		bt_id_error_message("internal error, q_index= %d but num_dofs %d\n", q_index, m_num_dofs);
-		return -1;
-	}
-
-	m_child_indices.resize(m_body_list.size());
-
-	for (idArrayIdx child = 1; child < m_parent_index.size(); child++)
-	{
-		const int &parent = m_parent_index[child];
-		if (parent >= 0 && parent < (static_cast<int>(m_parent_index.size()) - 1))
-		{
-			m_child_indices[parent].push_back(child);
-		}
-		else
-		{
-			if (-1 == parent)
-			{
-				// multiple bodies are directly linked to the environment, ie, not a single root
-				bt_id_error_message("building index sets parent(%zu)= -1 (multiple roots)\n", child);
-			}
-			else
-			{
-				// should never happen
-				bt_id_error_message(
-					"building index sets. parent_index[%zu]= %d, but m_parent_index.size()= %d\n",
-					child, parent, static_cast<int>(m_parent_index.size()));
-			}
-			return -1;
-		}
-	}
-
-	return 0;
-}
-
-void MultiBodyTree::MultiBodyImpl::calculateStaticData()
-{
-	// relative kinematics that are not a function of q, u, dot_u
-	for (idArrayIdx i = 0; i < m_body_list.size(); i++)
-	{
-		RigidBody &body = m_body_list[i];
-		switch (body.m_joint_type)
-		{
-			case REVOLUTE:
-				body.m_parent_vel_rel(0) = 0;
-				body.m_parent_vel_rel(1) = 0;
-				body.m_parent_vel_rel(2) = 0;
-				body.m_parent_acc_rel(0) = 0;
-				body.m_parent_acc_rel(1) = 0;
-				body.m_parent_acc_rel(2) = 0;
-				body.m_parent_pos_parent_body = body.m_parent_pos_parent_body_ref;
-				break;
-			case PRISMATIC:
-				body.m_body_T_parent = body.m_body_T_parent_ref;
-				body.m_parent_Jac_JT = body.m_body_T_parent_ref.transpose() * body.m_Jac_JT;
-				body.m_body_ang_vel_rel(0) = 0;
-				body.m_body_ang_vel_rel(1) = 0;
-				body.m_body_ang_vel_rel(2) = 0;
-				body.m_body_ang_acc_rel(0) = 0;
-				body.m_body_ang_acc_rel(1) = 0;
-				body.m_body_ang_acc_rel(2) = 0;
-				break;
-			case FIXED:
-				body.m_parent_pos_parent_body = body.m_parent_pos_parent_body_ref;
-				body.m_body_T_parent = body.m_body_T_parent_ref;
-				body.m_body_ang_vel_rel(0) = 0;
-				body.m_body_ang_vel_rel(1) = 0;
-				body.m_body_ang_vel_rel(2) = 0;
-				body.m_parent_vel_rel(0) = 0;
-				body.m_parent_vel_rel(1) = 0;
-				body.m_parent_vel_rel(2) = 0;
-				body.m_body_ang_acc_rel(0) = 0;
-				body.m_body_ang_acc_rel(1) = 0;
-				body.m_body_ang_acc_rel(2) = 0;
-				body.m_parent_acc_rel(0) = 0;
-				body.m_parent_acc_rel(1) = 0;
-				body.m_parent_acc_rel(2) = 0;
-				break;
-			case FLOATING:
-				// no static data
-				break;
-			case SPHERICAL:
-				//todo: review
-				body.m_parent_pos_parent_body = body.m_parent_pos_parent_body_ref;
-				body.m_parent_vel_rel(0) = 0;
-				body.m_parent_vel_rel(1) = 0;
-				body.m_parent_vel_rel(2) = 0;
-				body.m_parent_acc_rel(0) = 0;
-				body.m_parent_acc_rel(1) = 0;
-				body.m_parent_acc_rel(2) = 0;
-				break;
-		}
-
-			// resize & initialize jacobians to zero.
-#if (defined BT_ID_HAVE_MAT3X) && (defined BT_ID_WITH_JACOBIANS)
-		body.m_body_dot_Jac_T_u(0) = 0.0;
-		body.m_body_dot_Jac_T_u(1) = 0.0;
-		body.m_body_dot_Jac_T_u(2) = 0.0;
-		body.m_body_dot_Jac_R_u(0) = 0.0;
-		body.m_body_dot_Jac_R_u(1) = 0.0;
-		body.m_body_dot_Jac_R_u(2) = 0.0;
-		resize(body.m_body_Jac_T, m_num_dofs);
-		resize(body.m_body_Jac_R, m_num_dofs);
-		body.m_body_Jac_T.setZero();
-		body.m_body_Jac_R.setZero();
-#endif  //
-	}
-}
-
-int MultiBodyTree::MultiBodyImpl::calculateInverseDynamics(const vecx &q, const vecx &u,
-														   const vecx &dot_u, vecx *joint_forces)
-{
-	if (q.size() != m_num_dofs || u.size() != m_num_dofs || dot_u.size() != m_num_dofs ||
-		joint_forces->size() != m_num_dofs)
-	{
-		bt_id_error_message(
-			"wrong vector dimension. system has %d DOFs,\n"
-			"but dim(q)= %d, dim(u)= %d, dim(dot_u)= %d, dim(joint_forces)= %d\n",
-			m_num_dofs, static_cast<int>(q.size()), static_cast<int>(u.size()),
-			static_cast<int>(dot_u.size()), static_cast<int>(joint_forces->size()));
-		return -1;
-	}
-	// 1. relative kinematics
-	if (-1 == calculateKinematics(q, u, dot_u, POSITION_VELOCITY_ACCELERATION))
-	{
-		bt_id_error_message("error in calculateKinematics\n");
-		return -1;
-	}
-	// 2. update contributions to equations of motion for every body.
-	for (idArrayIdx i = 0; i < m_body_list.size(); i++)
-	{
-		RigidBody &body = m_body_list[i];
-		// 3.4 update dynamic terms (rate of change of angular & linear momentum)
-		body.m_eom_lhs_rotational =
-			body.m_body_I_body * body.m_body_ang_acc + body.m_body_mass_com.cross(body.m_body_acc) +
-			body.m_body_ang_vel.cross(body.m_body_I_body * body.m_body_ang_vel) -
-			body.m_body_moment_user;
-		body.m_eom_lhs_translational =
-			body.m_body_ang_acc.cross(body.m_body_mass_com) + body.m_mass * body.m_body_acc +
-			body.m_body_ang_vel.cross(body.m_body_ang_vel.cross(body.m_body_mass_com)) -
-			body.m_body_force_user;
-	}
-
-	// 3. calculate full set of forces at parent joint
-	// (not directly calculating the joint force along the free direction
-	// simplifies inclusion of fixed joints.
-	// An alternative would be to fuse bodies in a pre-processing step,
-	// but that would make changing masses online harder (eg, payload masses
-	// added with fixed  joints to a gripper)
-	// Also, this enables adding zero weight bodies as a way to calculate frame poses
-	// for force elements, etc.
-
-	for (int body_idx = m_body_list.size() - 1; body_idx >= 0; body_idx--)
-	{
-		// sum of forces and moments acting on this body from its children
-		vec3 sum_f_children;
-		vec3 sum_m_children;
-		setZero(sum_f_children);
-		setZero(sum_m_children);
-		for (idArrayIdx child_list_idx = 0; child_list_idx < m_child_indices[body_idx].size();
-			 child_list_idx++)
-		{
-			const RigidBody &child = m_body_list[m_child_indices[body_idx][child_list_idx]];
-			vec3 child_joint_force_in_this_frame =
-				child.m_body_T_parent.transpose() * child.m_force_at_joint;
-			sum_f_children -= child_joint_force_in_this_frame;
-			sum_m_children -= child.m_body_T_parent.transpose() * child.m_moment_at_joint +
-							  child.m_parent_pos_parent_body.cross(child_joint_force_in_this_frame);
-		}
-		RigidBody &body = m_body_list[body_idx];
-
-		body.m_force_at_joint = body.m_eom_lhs_translational - sum_f_children;
-		body.m_moment_at_joint = body.m_eom_lhs_rotational - sum_m_children;
-	}
-
-	// 4. Calculate Joint forces.
-	// These are the components of force_at_joint/moment_at_joint
-	// in the free directions given by Jac_JT/Jac_JR
-	// 4.1 revolute joints
-	for (idArrayIdx i = 0; i < m_body_revolute_list.size(); i++)
-	{
-		RigidBody &body = m_body_list[m_body_revolute_list[i]];
-		// (*joint_forces)(body.m_q_index) = body.m_Jac_JR.transpose() * body.m_moment_at_joint;
-		(*joint_forces)(body.m_q_index) = body.m_Jac_JR.dot(body.m_moment_at_joint);
-	}
-	// 4.2 for prismatic joints
-	for (idArrayIdx i = 0; i < m_body_prismatic_list.size(); i++)
-	{
-		RigidBody &body = m_body_list[m_body_prismatic_list[i]];
-		// (*joint_forces)(body.m_q_index) = body.m_Jac_JT.transpose() * body.m_force_at_joint;
-		(*joint_forces)(body.m_q_index) = body.m_Jac_JT.dot(body.m_force_at_joint);
-	}
-	// 4.3 floating bodies (6-DoF joints)
-	for (idArrayIdx i = 0; i < m_body_floating_list.size(); i++)
-	{
-		RigidBody &body = m_body_list[m_body_floating_list[i]];
-		(*joint_forces)(body.m_q_index + 0) = body.m_moment_at_joint(0);
-		(*joint_forces)(body.m_q_index + 1) = body.m_moment_at_joint(1);
-		(*joint_forces)(body.m_q_index + 2) = body.m_moment_at_joint(2);
-
-		(*joint_forces)(body.m_q_index + 3) = body.m_force_at_joint(0);
-		(*joint_forces)(body.m_q_index + 4) = body.m_force_at_joint(1);
-		(*joint_forces)(body.m_q_index + 5) = body.m_force_at_joint(2);
-	}
-
-	// 4.4 spherical bodies (3-DoF joints)
-	for (idArrayIdx i = 0; i < m_body_spherical_list.size(); i++)
-	{
-		//todo: review
-		RigidBody &body = m_body_list[m_body_spherical_list[i]];
-		(*joint_forces)(body.m_q_index + 0) = body.m_moment_at_joint(0);
-		(*joint_forces)(body.m_q_index + 1) = body.m_moment_at_joint(1);
-		(*joint_forces)(body.m_q_index + 2) = body.m_moment_at_joint(2);
-	}
-	return 0;
-}
-
-int MultiBodyTree::MultiBodyImpl::calculateKinematics(const vecx &q, const vecx &u, const vecx &dot_u,
-													  const KinUpdateType type)
-{
-	if (q.size() != m_num_dofs || u.size() != m_num_dofs || dot_u.size() != m_num_dofs)
-	{
-		bt_id_error_message(
-			"wrong vector dimension. system has %d DOFs,\n"
-			"but dim(q)= %d, dim(u)= %d, dim(dot_u)= %d\n",
-			m_num_dofs, static_cast<int>(q.size()), static_cast<int>(u.size()),
-			static_cast<int>(dot_u.size()));
-		return -1;
-	}
-	if (type != POSITION_ONLY && type != POSITION_VELOCITY && type != POSITION_VELOCITY_ACCELERATION)
-	{
-		bt_id_error_message("invalid type %d\n", type);
-		return -1;
-	}
-
-	// 1. update relative kinematics
-	// 1.1 for revolute
-	for (idArrayIdx i = 0; i < m_body_revolute_list.size(); i++)
-	{
-		RigidBody &body = m_body_list[m_body_revolute_list[i]];
-		mat33 T;
-		bodyTParentFromAxisAngle(body.m_Jac_JR, q(body.m_q_index), &T);
-		body.m_body_T_parent = T * body.m_body_T_parent_ref;
-		if (type >= POSITION_VELOCITY)
-		{
-			body.m_body_ang_vel_rel = body.m_Jac_JR * u(body.m_q_index);
-		}
-		if (type >= POSITION_VELOCITY_ACCELERATION)
-		{
-			body.m_body_ang_acc_rel = body.m_Jac_JR * dot_u(body.m_q_index);
-		}
-	}
-	// 1.2 for prismatic
-	for (idArrayIdx i = 0; i < m_body_prismatic_list.size(); i++)
-	{
-		RigidBody &body = m_body_list[m_body_prismatic_list[i]];
-		body.m_parent_pos_parent_body =
-			body.m_parent_pos_parent_body_ref + body.m_parent_Jac_JT * q(body.m_q_index);
-		if (type >= POSITION_VELOCITY)
-		{
-			body.m_parent_vel_rel =
-				body.m_body_T_parent_ref.transpose() * body.m_Jac_JT * u(body.m_q_index);
-		}
-		if (type >= POSITION_VELOCITY_ACCELERATION)
-		{
-			body.m_parent_acc_rel = body.m_parent_Jac_JT * dot_u(body.m_q_index);
-		}
-	}
-	// 1.3 fixed joints: nothing to do
-	// 1.4 6dof joints:
-	for (idArrayIdx i = 0; i < m_body_floating_list.size(); i++)
-	{
-		RigidBody &body = m_body_list[m_body_floating_list[i]];
-
-		body.m_body_T_parent = transformZ(q(body.m_q_index + 2)) *
-							   transformY(q(body.m_q_index + 1)) *
-							   transformX(q(body.m_q_index));
-		body.m_parent_pos_parent_body(0) = q(body.m_q_index + 3);
-		body.m_parent_pos_parent_body(1) = q(body.m_q_index + 4);
-		body.m_parent_pos_parent_body(2) = q(body.m_q_index + 5);
-		body.m_parent_pos_parent_body = body.m_body_T_parent * body.m_parent_pos_parent_body;
-
-		if (type >= POSITION_VELOCITY)
-		{
-			body.m_body_ang_vel_rel(0) = u(body.m_q_index + 0);
-			body.m_body_ang_vel_rel(1) = u(body.m_q_index + 1);
-			body.m_body_ang_vel_rel(2) = u(body.m_q_index + 2);
-
-			body.m_parent_vel_rel(0) = u(body.m_q_index + 3);
-			body.m_parent_vel_rel(1) = u(body.m_q_index + 4);
-			body.m_parent_vel_rel(2) = u(body.m_q_index + 5);
-
-			body.m_parent_vel_rel = body.m_body_T_parent.transpose() * body.m_parent_vel_rel;
-		}
-		if (type >= POSITION_VELOCITY_ACCELERATION)
-		{
-			body.m_body_ang_acc_rel(0) = dot_u(body.m_q_index + 0);
-			body.m_body_ang_acc_rel(1) = dot_u(body.m_q_index + 1);
-			body.m_body_ang_acc_rel(2) = dot_u(body.m_q_index + 2);
-
-			body.m_parent_acc_rel(0) = dot_u(body.m_q_index + 3);
-			body.m_parent_acc_rel(1) = dot_u(body.m_q_index + 4);
-			body.m_parent_acc_rel(2) = dot_u(body.m_q_index + 5);
-
-			body.m_parent_acc_rel = body.m_body_T_parent.transpose() * body.m_parent_acc_rel;
-		}
-	}
-	
-	for (idArrayIdx i = 0; i < m_body_spherical_list.size(); i++)
-	{
-		//todo: review
-		RigidBody &body = m_body_list[m_body_spherical_list[i]];
-
-		mat33 T;
-
-		T = transformX(q(body.m_q_index)) *
-				transformY(q(body.m_q_index + 1)) *
-				transformZ(q(body.m_q_index + 2));
-		body.m_body_T_parent = T * body.m_body_T_parent_ref;
-			
-		body.m_parent_pos_parent_body(0)=0;
-		body.m_parent_pos_parent_body(1)=0;
-		body.m_parent_pos_parent_body(2)=0;
-		
-		body.m_parent_pos_parent_body = body.m_body_T_parent * body.m_parent_pos_parent_body;
-
-		if (type >= POSITION_VELOCITY)
-		{
-			body.m_body_ang_vel_rel(0) = u(body.m_q_index + 0);
-			body.m_body_ang_vel_rel(1) = u(body.m_q_index + 1);
-			body.m_body_ang_vel_rel(2) = u(body.m_q_index + 2);
-			body.m_parent_vel_rel = body.m_body_T_parent.transpose() * body.m_parent_vel_rel;
-		}
-		if (type >= POSITION_VELOCITY_ACCELERATION)
-		{
-			body.m_body_ang_acc_rel(0) = dot_u(body.m_q_index + 0);
-			body.m_body_ang_acc_rel(1) = dot_u(body.m_q_index + 1);
-			body.m_body_ang_acc_rel(2) = dot_u(body.m_q_index + 2);
-			body.m_parent_acc_rel = body.m_body_T_parent.transpose() * body.m_parent_acc_rel;
-		}
-	}
-
-	// 2. absolute kinematic quantities (vector valued)
-	// NOTE: this should be optimized by specializing for different body types
-	// (e.g., relative rotation is always zero for prismatic joints, etc.)
-
-	// calculations for root body
-	{
-		RigidBody &body = m_body_list[0];
-		// 3.1 update absolute positions and orientations:
-		// will be required if we add force elements (eg springs between bodies,
-		// or contacts)
-		// not required right now, added here for debugging purposes
-		body.m_body_pos = body.m_body_T_parent * body.m_parent_pos_parent_body;
-		body.m_body_T_world = body.m_body_T_parent;
-
-		if (type >= POSITION_VELOCITY)
-		{
-			// 3.2 update absolute velocities
-			body.m_body_ang_vel = body.m_body_ang_vel_rel;
-			body.m_body_vel = body.m_parent_vel_rel;
-		}
-		if (type >= POSITION_VELOCITY_ACCELERATION)
-		{
-			// 3.3 update absolute accelerations
-			// NOTE: assumption: dot(J_JR) = 0; true here, but not for general joints
-			body.m_body_ang_acc = body.m_body_ang_acc_rel;
-			body.m_body_acc = body.m_body_T_parent * body.m_parent_acc_rel;
-			// add gravitational acceleration to root body
-			// this is an efficient way to add gravitational terms,
-			// but it does mean that the kinematics are no longer
-			// correct at the acceleration level
-			// NOTE: To get correct acceleration kinematics, just set world_gravity to zero
-			body.m_body_acc = body.m_body_acc - body.m_body_T_parent * m_world_gravity;
-		}
-	}
-
-	for (idArrayIdx i = 1; i < m_body_list.size(); i++)
-	{
-		RigidBody &body = m_body_list[i];
-		RigidBody &parent = m_body_list[m_parent_index[i]];
-		// 2.1 update absolute positions and orientations:
-		// will be required if we add force elements (eg springs between bodies,
-		// or contacts)  not required right now added here for debugging purposes
-		body.m_body_pos =
-			body.m_body_T_parent * (parent.m_body_pos + body.m_parent_pos_parent_body);
-		body.m_body_T_world = body.m_body_T_parent * parent.m_body_T_world;
-
-		if (type >= POSITION_VELOCITY)
-		{
-			// 2.2 update absolute velocities
-			body.m_body_ang_vel =
-				body.m_body_T_parent * parent.m_body_ang_vel + body.m_body_ang_vel_rel;
-
-			body.m_body_vel =
-				body.m_body_T_parent *
-				(parent.m_body_vel + parent.m_body_ang_vel.cross(body.m_parent_pos_parent_body) +
-				 body.m_parent_vel_rel);
-		}
-		if (type >= POSITION_VELOCITY_ACCELERATION)
-		{
-			// 2.3 update absolute accelerations
-			// NOTE: assumption: dot(J_JR) = 0; true here, but not for general joints
-			body.m_body_ang_acc =
-				body.m_body_T_parent * parent.m_body_ang_acc -
-				body.m_body_ang_vel_rel.cross(body.m_body_T_parent * parent.m_body_ang_vel) +
-				body.m_body_ang_acc_rel;
-			body.m_body_acc =
-				body.m_body_T_parent *
-				(parent.m_body_acc + parent.m_body_ang_acc.cross(body.m_parent_pos_parent_body) +
-				 parent.m_body_ang_vel.cross(parent.m_body_ang_vel.cross(body.m_parent_pos_parent_body)) +
-				 2.0 * parent.m_body_ang_vel.cross(body.m_parent_vel_rel) + body.m_parent_acc_rel);
-		}
-	}
-
-	return 0;
-}
-
-#if (defined BT_ID_HAVE_MAT3X) && (defined BT_ID_WITH_JACOBIANS)
-
-void MultiBodyTree::MultiBodyImpl::addRelativeJacobianComponent(RigidBody &body)
-{
-	const int &idx = body.m_q_index;
-	switch (body.m_joint_type)
-	{
-		case FIXED:
-			break;
-		case REVOLUTE:
-			setMat3xElem(0, idx, body.m_Jac_JR(0), &body.m_body_Jac_R);
-			setMat3xElem(1, idx, body.m_Jac_JR(1), &body.m_body_Jac_R);
-			setMat3xElem(2, idx, body.m_Jac_JR(2), &body.m_body_Jac_R);
-			break;
-		case PRISMATIC:
-			setMat3xElem(0, idx, body.m_body_T_parent_ref(0, 0) * body.m_Jac_JT(0) + body.m_body_T_parent_ref(1, 0) * body.m_Jac_JT(1) + body.m_body_T_parent_ref(2, 0) * body.m_Jac_JT(2),
-						 &body.m_body_Jac_T);
-			setMat3xElem(1, idx, body.m_body_T_parent_ref(0, 1) * body.m_Jac_JT(0) + body.m_body_T_parent_ref(1, 1) * body.m_Jac_JT(1) + body.m_body_T_parent_ref(2, 1) * body.m_Jac_JT(2),
-						 &body.m_body_Jac_T);
-			setMat3xElem(2, idx, body.m_body_T_parent_ref(0, 2) * body.m_Jac_JT(0) + body.m_body_T_parent_ref(1, 2) * body.m_Jac_JT(1) + body.m_body_T_parent_ref(2, 2) * body.m_Jac_JT(2),
-						 &body.m_body_Jac_T);
-			break;
-		case FLOATING:
-			setMat3xElem(0, idx + 0, 1.0, &body.m_body_Jac_R);
-			setMat3xElem(1, idx + 1, 1.0, &body.m_body_Jac_R);
-			setMat3xElem(2, idx + 2, 1.0, &body.m_body_Jac_R);
-			// body_Jac_T = body_T_parent.transpose();
-			setMat3xElem(0, idx + 3, body.m_body_T_parent(0, 0), &body.m_body_Jac_T);
-			setMat3xElem(0, idx + 4, body.m_body_T_parent(1, 0), &body.m_body_Jac_T);
-			setMat3xElem(0, idx + 5, body.m_body_T_parent(2, 0), &body.m_body_Jac_T);
-
-			setMat3xElem(1, idx + 3, body.m_body_T_parent(0, 1), &body.m_body_Jac_T);
-			setMat3xElem(1, idx + 4, body.m_body_T_parent(1, 1), &body.m_body_Jac_T);
-			setMat3xElem(1, idx + 5, body.m_body_T_parent(2, 1), &body.m_body_Jac_T);
-
-			setMat3xElem(2, idx + 3, body.m_body_T_parent(0, 2), &body.m_body_Jac_T);
-			setMat3xElem(2, idx + 4, body.m_body_T_parent(1, 2), &body.m_body_Jac_T);
-			setMat3xElem(2, idx + 5, body.m_body_T_parent(2, 2), &body.m_body_Jac_T);
-
-			break;
-		case SPHERICAL:
-			//todo: review
-			setMat3xElem(0, idx + 0, 1.0, &body.m_body_Jac_R);
-			setMat3xElem(1, idx + 1, 1.0, &body.m_body_Jac_R);
-			setMat3xElem(2, idx + 2, 1.0, &body.m_body_Jac_R);
-			break;
-	}
-}
-
-int MultiBodyTree::MultiBodyImpl::calculateJacobians(const vecx &q, const vecx &u, const KinUpdateType type)
-{
-	if (q.size() != m_num_dofs || u.size() != m_num_dofs)
-	{
-		bt_id_error_message(
-			"wrong vector dimension. system has %d DOFs,\n"
-			"but dim(q)= %d, dim(u)= %d\n",
-			m_num_dofs, static_cast<int>(q.size()), static_cast<int>(u.size()));
-		return -1;
-	}
-	if (type != POSITION_ONLY && type != POSITION_VELOCITY)
-	{
-		bt_id_error_message("invalid type %d\n", type);
-		return -1;
-	}
-
-	addRelativeJacobianComponent(m_body_list[0]);
-	for (idArrayIdx i = 1; i < m_body_list.size(); i++)
-	{
-		RigidBody &body = m_body_list[i];
-		RigidBody &parent = m_body_list[m_parent_index[i]];
-
-		mul(body.m_body_T_parent, parent.m_body_Jac_R, &body.m_body_Jac_R);
-		body.m_body_Jac_T = parent.m_body_Jac_T;
-		mul(tildeOperator(body.m_parent_pos_parent_body), parent.m_body_Jac_R, &m_m3x);
-		sub(body.m_body_Jac_T, m_m3x, &body.m_body_Jac_T);
-
-		addRelativeJacobianComponent(body);
-		mul(body.m_body_T_parent, body.m_body_Jac_T, &body.m_body_Jac_T);
-
-		if (type >= POSITION_VELOCITY)
-		{
-			body.m_body_dot_Jac_R_u = body.m_body_T_parent * parent.m_body_dot_Jac_R_u -
-									  body.m_body_ang_vel_rel.cross(body.m_body_T_parent * parent.m_body_ang_vel);
-			body.m_body_dot_Jac_T_u = body.m_body_T_parent *
-									  (parent.m_body_dot_Jac_T_u + parent.m_body_dot_Jac_R_u.cross(body.m_parent_pos_parent_body) +
-									   parent.m_body_ang_vel.cross(parent.m_body_ang_vel.cross(body.m_parent_pos_parent_body)) +
-									   2.0 * parent.m_body_ang_vel.cross(body.m_parent_vel_rel));
-		}
-	}
-	return 0;
-}
-#endif
-
-static inline void setThreeDoFJacobians(const int dof, vec3 &Jac_JR, vec3 &Jac_JT)
-{
-	switch (dof)
-	{
-		// rotational part
-		case 0:
-			Jac_JR(0) = 1;
-			Jac_JR(1) = 0;
-			Jac_JR(2) = 0;
-			setZero(Jac_JT);
-			break;
-		case 1:
-			Jac_JR(0) = 0;
-			Jac_JR(1) = 1;
-			Jac_JR(2) = 0;
-			setZero(Jac_JT);
-			break;
-		case 2:
-			Jac_JR(0) = 0;
-			Jac_JR(1) = 0;
-			Jac_JR(2) = 1;
-			setZero(Jac_JT);
-			break;
-	}
-}
-
-static inline void setSixDoFJacobians(const int dof, vec3 &Jac_JR, vec3 &Jac_JT)
-{
-	switch (dof)
-	{
-		// rotational part
-		case 0:
-			Jac_JR(0) = 1;
-			Jac_JR(1) = 0;
-			Jac_JR(2) = 0;
-			setZero(Jac_JT);
-			break;
-		case 1:
-			Jac_JR(0) = 0;
-			Jac_JR(1) = 1;
-			Jac_JR(2) = 0;
-			setZero(Jac_JT);
-			break;
-		case 2:
-			Jac_JR(0) = 0;
-			Jac_JR(1) = 0;
-			Jac_JR(2) = 1;
-			setZero(Jac_JT);
-			break;
-		// translational part
-		case 3:
-			setZero(Jac_JR);
-			Jac_JT(0) = 1;
-			Jac_JT(1) = 0;
-			Jac_JT(2) = 0;
-			break;
-		case 4:
-			setZero(Jac_JR);
-			Jac_JT(0) = 0;
-			Jac_JT(1) = 1;
-			Jac_JT(2) = 0;
-			break;
-		case 5:
-			setZero(Jac_JR);
-			Jac_JT(0) = 0;
-			Jac_JT(1) = 0;
-			Jac_JT(2) = 1;
-			break;
-	}
-}
-
-static inline int jointNumDoFs(const JointType &type)
-{
-	switch (type)
-	{
-		case FIXED:
-			return 0;
-		case REVOLUTE:
-		case PRISMATIC:
-			return 1;
-		case FLOATING:
-			return 6;
-		case SPHERICAL:
-			return 3;
-	}
-	// this should never happen
-	bt_id_error_message("invalid joint type\n");
-	// TODO add configurable abort/crash function
-	abort();
-	return 0;
-}
-
-int MultiBodyTree::MultiBodyImpl::calculateMassMatrix(const vecx &q, const bool update_kinematics,
-													  const bool initialize_matrix,
-													  const bool set_lower_triangular_matrix,
-													  matxx *mass_matrix)
-{
-	// This calculates the joint space mass matrix for the multibody system.
-	// The algorithm is essentially an implementation of "method 3"
-	// in "Efficient Dynamic Simulation of Robotic Mechanisms" (Walker and Orin, 1982)
-	// (Later named "Composite Rigid Body Algorithm" by Featherstone).
-	//
-	// This implementation, however, handles branched systems and uses a formulation centered
-	// on the origin of the body-fixed frame to avoid re-computing various quantities at the com.
-
-	if (q.size() != m_num_dofs || mass_matrix->rows() != m_num_dofs ||
-		mass_matrix->cols() != m_num_dofs)
-	{
-		bt_id_error_message(
-			"Dimension error. System has %d DOFs,\n"
-			"but dim(q)= %d, dim(mass_matrix)= %d x %d\n",
-			m_num_dofs, static_cast<int>(q.size()), static_cast<int>(mass_matrix->rows()),
-			static_cast<int>(mass_matrix->cols()));
-		return -1;
-	}
-
-	// TODO add optimized zeroing function?
-	if (initialize_matrix)
-	{
-		for (int i = 0; i < m_num_dofs; i++)
-		{
-			for (int j = 0; j < m_num_dofs; j++)
-			{
-				setMatxxElem(i, j, 0.0, mass_matrix);
-			}
-		}
-	}
-
-	if (update_kinematics)
-	{
-		// 1. update relative kinematics
-		// 1.1 for revolute joints
-		for (idArrayIdx i = 0; i < m_body_revolute_list.size(); i++)
-		{
-			RigidBody &body = m_body_list[m_body_revolute_list[i]];
-			// from reference orientation (q=0) of body-fixed frame to current orientation
-			mat33 body_T_body_ref;
-			bodyTParentFromAxisAngle(body.m_Jac_JR, q(body.m_q_index), &body_T_body_ref);
-			body.m_body_T_parent = body_T_body_ref * body.m_body_T_parent_ref;
-		}
-		// 1.2 for prismatic joints
-		for (idArrayIdx i = 0; i < m_body_prismatic_list.size(); i++)
-		{
-			RigidBody &body = m_body_list[m_body_prismatic_list[i]];
-			// body.m_body_T_parent= fixed
-			body.m_parent_pos_parent_body =
-				body.m_parent_pos_parent_body_ref + body.m_parent_Jac_JT * q(body.m_q_index);
-		}
-		// 1.3 fixed joints: nothing to do
-		// 1.4 6dof joints:
-		for (idArrayIdx i = 0; i < m_body_floating_list.size(); i++)
-		{
-			RigidBody &body = m_body_list[m_body_floating_list[i]];
-
-			body.m_body_T_parent = transformZ(q(body.m_q_index + 2)) *
-								   transformY(q(body.m_q_index + 1)) *
-								   transformX(q(body.m_q_index));
-			body.m_parent_pos_parent_body(0) = q(body.m_q_index + 3);
-			body.m_parent_pos_parent_body(1) = q(body.m_q_index + 4);
-			body.m_parent_pos_parent_body(2) = q(body.m_q_index + 5);
-
-			body.m_parent_pos_parent_body = body.m_body_T_parent * body.m_parent_pos_parent_body;
-		}
-
-		for (idArrayIdx i = 0; i < m_body_spherical_list.size(); i++)
-		{
-			//todo: review
-			RigidBody &body = m_body_list[m_body_spherical_list[i]];
-
-			mat33 T;
-
-			T = transformX(q(body.m_q_index)) *
-				transformY(q(body.m_q_index + 1)) *
-				transformZ(q(body.m_q_index + 2));
-			body.m_body_T_parent = T * body.m_body_T_parent_ref;
-
-			body.m_parent_pos_parent_body(0)=0;
-			body.m_parent_pos_parent_body(1)=0;
-			body.m_parent_pos_parent_body(2)=0;
-			
-			body.m_parent_pos_parent_body = body.m_body_T_parent * body.m_parent_pos_parent_body;
-		}
-	}
-	for (int i = m_body_list.size() - 1; i >= 0; i--)
-	{
-		RigidBody &body = m_body_list[i];
-		// calculate mass, center of mass and inertia of "composite rigid body",
-		// ie, sub-tree starting at current body
-		body.m_subtree_mass = body.m_mass;
-		body.m_body_subtree_mass_com = body.m_body_mass_com;
-		body.m_body_subtree_I_body = body.m_body_I_body;
-
-		for (idArrayIdx c = 0; c < m_child_indices[i].size(); c++)
-		{
-			RigidBody &child = m_body_list[m_child_indices[i][c]];
-			mat33 body_T_child = child.m_body_T_parent.transpose();
-
-			body.m_subtree_mass += child.m_subtree_mass;
-			body.m_body_subtree_mass_com += body_T_child * child.m_body_subtree_mass_com +
-											child.m_parent_pos_parent_body * child.m_subtree_mass;
-			body.m_body_subtree_I_body +=
-				body_T_child * child.m_body_subtree_I_body * child.m_body_T_parent;
-
-			if (child.m_subtree_mass > 0)
-			{
-				// Shift the reference point for the child subtree inertia using the
-				// Huygens-Steiner ("parallel axis") theorem.
-				// (First shift from child origin to child com, then from there to this body's
-				// origin)
-				vec3 r_com = body_T_child * child.m_body_subtree_mass_com / child.m_subtree_mass;
-				mat33 tilde_r_child_com = tildeOperator(r_com);
-				mat33 tilde_r_body_com = tildeOperator(child.m_parent_pos_parent_body + r_com);
-				body.m_body_subtree_I_body +=
-					child.m_subtree_mass *
-					(tilde_r_child_com * tilde_r_child_com - tilde_r_body_com * tilde_r_body_com);
-			}
-		}
-	}
-
-	for (int i = m_body_list.size() - 1; i >= 0; i--)
-	{
-		const RigidBody &body = m_body_list[i];
-
-		// determine DoF-range for body
-		const int q_index_min = body.m_q_index;
-		const int q_index_max = q_index_min + jointNumDoFs(body.m_joint_type) - 1;
-		// loop over the DoFs used by this body
-		// local joint jacobians (ok as is for 1-DoF joints)
-		vec3 Jac_JR = body.m_Jac_JR;
-		vec3 Jac_JT = body.m_Jac_JT;
-		for (int col = q_index_max; col >= q_index_min; col--)
-		{
-			// set jacobians for 6-DoF joints
-			if (FLOATING == body.m_joint_type)
-			{
-				setSixDoFJacobians(col - q_index_min, Jac_JR, Jac_JT);
-			}
-			if (SPHERICAL == body.m_joint_type)
-			{
-				//todo: review
-				setThreeDoFJacobians(col - q_index_min, Jac_JR, Jac_JT);
-			}
-
-			vec3 body_eom_rot =
-				body.m_body_subtree_I_body * Jac_JR + body.m_body_subtree_mass_com.cross(Jac_JT);
-			vec3 body_eom_trans =
-				body.m_subtree_mass * Jac_JT - body.m_body_subtree_mass_com.cross(Jac_JR);
-			setMatxxElem(col, col, Jac_JR.dot(body_eom_rot) + Jac_JT.dot(body_eom_trans), mass_matrix);
-
-			// rest of the mass matrix column upwards
-			{
-				// 1. for multi-dof joints, rest of the dofs of this body
-				for (int row = col - 1; row >= q_index_min; row--)
-				{
-					if (SPHERICAL == body.m_joint_type)
-					{
-						//todo: review
-						setThreeDoFJacobians(row - q_index_min, Jac_JR, Jac_JT);
-						const double Mrc = Jac_JR.dot(body_eom_rot) + Jac_JT.dot(body_eom_trans);
-						setMatxxElem(col, row, Mrc, mass_matrix);
-					}
-					if (FLOATING == body.m_joint_type)
-					{
-						setSixDoFJacobians(row - q_index_min, Jac_JR, Jac_JT);
-						const double Mrc = Jac_JR.dot(body_eom_rot) + Jac_JT.dot(body_eom_trans);
-						setMatxxElem(col, row, Mrc, mass_matrix);
-					}
-				}
-				// 2. ancestor dofs
-				int child_idx = i;
-				int parent_idx = m_parent_index[i];
-				while (parent_idx >= 0)
-				{
-					const RigidBody &child_body = m_body_list[child_idx];
-					const RigidBody &parent_body = m_body_list[parent_idx];
-
-					const mat33 parent_T_child = child_body.m_body_T_parent.transpose();
-					body_eom_rot = parent_T_child * body_eom_rot;
-					body_eom_trans = parent_T_child * body_eom_trans;
-					body_eom_rot += child_body.m_parent_pos_parent_body.cross(body_eom_trans);
-
-					const int parent_body_q_index_min = parent_body.m_q_index;
-					const int parent_body_q_index_max =
-						parent_body_q_index_min + jointNumDoFs(parent_body.m_joint_type) - 1;
-					vec3 Jac_JR = parent_body.m_Jac_JR;
-					vec3 Jac_JT = parent_body.m_Jac_JT;
-					for (int row = parent_body_q_index_max; row >= parent_body_q_index_min; row--)
-					{
-						if (SPHERICAL == parent_body.m_joint_type)
-						{
-							//todo: review
-							setThreeDoFJacobians(row - parent_body_q_index_min, Jac_JR, Jac_JT);
-						}
-						// set jacobians for 6-DoF joints
-						if (FLOATING == parent_body.m_joint_type)
-						{
-							setSixDoFJacobians(row - parent_body_q_index_min, Jac_JR, Jac_JT);
-						}
-						const double Mrc = Jac_JR.dot(body_eom_rot) + Jac_JT.dot(body_eom_trans);
-						setMatxxElem(col, row, Mrc, mass_matrix);
-					}
-
-					child_idx = parent_idx;
-					parent_idx = m_parent_index[child_idx];
-				}
-			}
-		}
-	}
-
-	if (set_lower_triangular_matrix)
-	{
-		for (int col = 0; col < m_num_dofs; col++)
-		{
-			for (int row = 0; row < col; row++)
-			{
-				setMatxxElem(row, col, (*mass_matrix)(col, row), mass_matrix);
-			}
-		}
-	}
-	return 0;
-}
-
-// utility macro
-#define CHECK_IF_BODY_INDEX_IS_VALID(index)                                                  \
-	do                                                                                       \
-	{                                                                                        \
-		if (index < 0 || index >= m_num_bodies)                                              \
-		{                                                                                    \
-			bt_id_error_message("invalid index %d (num_bodies= %d)\n", index, m_num_bodies); \
-			return -1;                                                                       \
-		}                                                                                    \
-	} while (0)
-
-int MultiBodyTree::MultiBodyImpl::getParentIndex(const int body_index, int *p)
-{
-	CHECK_IF_BODY_INDEX_IS_VALID(body_index);
-	*p = m_parent_index[body_index];
-	return 0;
-}
-
-int MultiBodyTree::MultiBodyImpl::getUserInt(const int body_index, int *user_int) const
-{
-	CHECK_IF_BODY_INDEX_IS_VALID(body_index);
-	*user_int = m_user_int[body_index];
-	return 0;
-}
-int MultiBodyTree::MultiBodyImpl::getUserPtr(const int body_index, void **user_ptr) const
-{
-	CHECK_IF_BODY_INDEX_IS_VALID(body_index);
-	*user_ptr = m_user_ptr[body_index];
-	return 0;
-}
-
-int MultiBodyTree::MultiBodyImpl::setUserInt(const int body_index, const int user_int)
-{
-	CHECK_IF_BODY_INDEX_IS_VALID(body_index);
-	m_user_int[body_index] = user_int;
-	return 0;
-}
-
-int MultiBodyTree::MultiBodyImpl::setUserPtr(const int body_index, void *const user_ptr)
-{
-	CHECK_IF_BODY_INDEX_IS_VALID(body_index);
-	m_user_ptr[body_index] = user_ptr;
-	return 0;
-}
-
-int MultiBodyTree::MultiBodyImpl::getBodyOrigin(int body_index, vec3 *world_origin) const
-{
-	CHECK_IF_BODY_INDEX_IS_VALID(body_index);
-	const RigidBody &body = m_body_list[body_index];
-	*world_origin = body.m_body_T_world.transpose() * body.m_body_pos;
-	return 0;
-}
-
-int MultiBodyTree::MultiBodyImpl::getBodyCoM(int body_index, vec3 *world_com) const
-{
-	CHECK_IF_BODY_INDEX_IS_VALID(body_index);
-	const RigidBody &body = m_body_list[body_index];
-	if (body.m_mass > 0)
-	{
-		*world_com = body.m_body_T_world.transpose() *
-					 (body.m_body_pos + body.m_body_mass_com / body.m_mass);
-	}
-	else
-	{
-		*world_com = body.m_body_T_world.transpose() * (body.m_body_pos);
-	}
-	return 0;
-}
-
-int MultiBodyTree::MultiBodyImpl::getBodyTransform(int body_index, mat33 *world_T_body) const
-{
-	CHECK_IF_BODY_INDEX_IS_VALID(body_index);
-	const RigidBody &body = m_body_list[body_index];
-	*world_T_body = body.m_body_T_world.transpose();
-	return 0;
-}
-int MultiBodyTree::MultiBodyImpl::getBodyAngularVelocity(int body_index, vec3 *world_omega) const
-{
-	CHECK_IF_BODY_INDEX_IS_VALID(body_index);
-	const RigidBody &body = m_body_list[body_index];
-	*world_omega = body.m_body_T_world.transpose() * body.m_body_ang_vel;
-	return 0;
-}
-int MultiBodyTree::MultiBodyImpl::getBodyLinearVelocity(int body_index,
-														vec3 *world_velocity) const
-{
-	CHECK_IF_BODY_INDEX_IS_VALID(body_index);
-	const RigidBody &body = m_body_list[body_index];
-	*world_velocity = body.m_body_T_world.transpose() * body.m_body_vel;
-	return 0;
-}
-
-int MultiBodyTree::MultiBodyImpl::getBodyLinearVelocityCoM(int body_index,
-														   vec3 *world_velocity) const
-{
-	CHECK_IF_BODY_INDEX_IS_VALID(body_index);
-	const RigidBody &body = m_body_list[body_index];
-	vec3 com;
-	if (body.m_mass > 0)
-	{
-		com = body.m_body_mass_com / body.m_mass;
-	}
-	else
-	{
-		com(0) = 0;
-		com(1) = 0;
-		com(2) = 0;
-	}
-
-	*world_velocity =
-		body.m_body_T_world.transpose() * (body.m_body_vel + body.m_body_ang_vel.cross(com));
-	return 0;
-}
-
-int MultiBodyTree::MultiBodyImpl::getBodyAngularAcceleration(int body_index,
-															 vec3 *world_dot_omega) const
-{
-	CHECK_IF_BODY_INDEX_IS_VALID(body_index);
-	const RigidBody &body = m_body_list[body_index];
-	*world_dot_omega = body.m_body_T_world.transpose() * body.m_body_ang_acc;
-	return 0;
-}
-int MultiBodyTree::MultiBodyImpl::getBodyLinearAcceleration(int body_index,
-															vec3 *world_acceleration) const
-{
-	CHECK_IF_BODY_INDEX_IS_VALID(body_index);
-	const RigidBody &body = m_body_list[body_index];
-	*world_acceleration = body.m_body_T_world.transpose() * body.m_body_acc;
-	return 0;
-}
-
-int MultiBodyTree::MultiBodyImpl::getJointType(const int body_index, JointType *joint_type) const
-{
-	CHECK_IF_BODY_INDEX_IS_VALID(body_index);
-	*joint_type = m_body_list[body_index].m_joint_type;
-	return 0;
-}
-
-int MultiBodyTree::MultiBodyImpl::getJointTypeStr(const int body_index,
-												  const char **joint_type) const
-{
-	CHECK_IF_BODY_INDEX_IS_VALID(body_index);
-	*joint_type = jointTypeToString(m_body_list[body_index].m_joint_type);
-	return 0;
-}
-
-int MultiBodyTree::MultiBodyImpl::getParentRParentBodyRef(const int body_index, vec3 *r) const
-{
-	CHECK_IF_BODY_INDEX_IS_VALID(body_index);
-	*r = m_body_list[body_index].m_parent_pos_parent_body_ref;
-	return 0;
-}
-
-int MultiBodyTree::MultiBodyImpl::getBodyTParentRef(const int body_index, mat33 *T) const
-{
-	CHECK_IF_BODY_INDEX_IS_VALID(body_index);
-	*T = m_body_list[body_index].m_body_T_parent_ref;
-	return 0;
-}
-
-int MultiBodyTree::MultiBodyImpl::getBodyAxisOfMotion(const int body_index, vec3 *axis) const
-{
-	CHECK_IF_BODY_INDEX_IS_VALID(body_index);
-	if (m_body_list[body_index].m_joint_type == REVOLUTE)
-	{
-		*axis = m_body_list[body_index].m_Jac_JR;
-		return 0;
-	}
-	if (m_body_list[body_index].m_joint_type == PRISMATIC)
-	{
-		*axis = m_body_list[body_index].m_Jac_JT;
-		return 0;
-	}
-	setZero(*axis);
-	return 0;
-}
-
-int MultiBodyTree::MultiBodyImpl::getDoFOffset(const int body_index, int *q_index) const
-{
-	CHECK_IF_BODY_INDEX_IS_VALID(body_index);
-	*q_index = m_body_list[body_index].m_q_index;
-	return 0;
-}
-
-int MultiBodyTree::MultiBodyImpl::setBodyMass(const int body_index, const idScalar mass)
-{
-	CHECK_IF_BODY_INDEX_IS_VALID(body_index);
-	m_body_list[body_index].m_mass = mass;
-	return 0;
-}
-
-int MultiBodyTree::MultiBodyImpl::setBodyFirstMassMoment(const int body_index,
-														 const vec3 &first_mass_moment)
-{
-	CHECK_IF_BODY_INDEX_IS_VALID(body_index);
-	m_body_list[body_index].m_body_mass_com = first_mass_moment;
-	return 0;
-}
-int MultiBodyTree::MultiBodyImpl::setBodySecondMassMoment(const int body_index,
-														  const mat33 &second_mass_moment)
-{
-	CHECK_IF_BODY_INDEX_IS_VALID(body_index);
-	m_body_list[body_index].m_body_I_body = second_mass_moment;
-	return 0;
-}
-int MultiBodyTree::MultiBodyImpl::getBodyMass(const int body_index, idScalar *mass) const
-{
-	CHECK_IF_BODY_INDEX_IS_VALID(body_index);
-	*mass = m_body_list[body_index].m_mass;
-	return 0;
-}
-int MultiBodyTree::MultiBodyImpl::getBodyFirstMassMoment(const int body_index,
-														 vec3 *first_mass_moment) const
-{
-	CHECK_IF_BODY_INDEX_IS_VALID(body_index);
-	*first_mass_moment = m_body_list[body_index].m_body_mass_com;
-	return 0;
-}
-int MultiBodyTree::MultiBodyImpl::getBodySecondMassMoment(const int body_index,
-														  mat33 *second_mass_moment) const
-{
-	CHECK_IF_BODY_INDEX_IS_VALID(body_index);
-	*second_mass_moment = m_body_list[body_index].m_body_I_body;
-	return 0;
-}
-
-void MultiBodyTree::MultiBodyImpl::clearAllUserForcesAndMoments()
-{
-	for (int index = 0; index < m_num_bodies; index++)
-	{
-		RigidBody &body = m_body_list[index];
-		setZero(body.m_body_force_user);
-		setZero(body.m_body_moment_user);
-	}
-}
-
-int MultiBodyTree::MultiBodyImpl::addUserForce(const int body_index, const vec3 &body_force)
-{
-	CHECK_IF_BODY_INDEX_IS_VALID(body_index);
-	m_body_list[body_index].m_body_force_user += body_force;
-	return 0;
-}
-
-int MultiBodyTree::MultiBodyImpl::addUserMoment(const int body_index, const vec3 &body_moment)
-{
-	CHECK_IF_BODY_INDEX_IS_VALID(body_index);
-	m_body_list[body_index].m_body_moment_user += body_moment;
-	return 0;
-}
-
-#if (defined BT_ID_HAVE_MAT3X) && (defined BT_ID_WITH_JACOBIANS)
-int MultiBodyTree::MultiBodyImpl::getBodyDotJacobianTransU(const int body_index, vec3 *world_dot_jac_trans_u) const
-{
-	CHECK_IF_BODY_INDEX_IS_VALID(body_index);
-	const RigidBody &body = m_body_list[body_index];
-	*world_dot_jac_trans_u = body.m_body_T_world.transpose() * body.m_body_dot_Jac_T_u;
-	return 0;
-}
-
-int MultiBodyTree::MultiBodyImpl::getBodyDotJacobianRotU(const int body_index, vec3 *world_dot_jac_rot_u) const
-{
-	CHECK_IF_BODY_INDEX_IS_VALID(body_index);
-	const RigidBody &body = m_body_list[body_index];
-	*world_dot_jac_rot_u = body.m_body_T_world.transpose() * body.m_body_dot_Jac_R_u;
-	return 0;
-}
-
-int MultiBodyTree::MultiBodyImpl::getBodyJacobianTrans(const int body_index, mat3x *world_jac_trans) const
-{
-	CHECK_IF_BODY_INDEX_IS_VALID(body_index);
-	const RigidBody &body = m_body_list[body_index];
-	mul(body.m_body_T_world.transpose(), body.m_body_Jac_T, world_jac_trans);
-	return 0;
-}
-
-int MultiBodyTree::MultiBodyImpl::getBodyJacobianRot(const int body_index, mat3x *world_jac_rot) const
-{
-	CHECK_IF_BODY_INDEX_IS_VALID(body_index);
-	const RigidBody &body = m_body_list[body_index];
-	mul(body.m_body_T_world.transpose(), body.m_body_Jac_R, world_jac_rot);
-	return 0;
-}
-
-#endif
-}  // namespace btInverseDynamics