chore: add more comments

src/dynamics/joint/multibody_joint/multibody.rs

@@ -569,8 +569,6 @@ impl Multibody {
             return; // Nothing to do.
         }
 
-        let mut kinematic_ndofs = 0;
-
         if self.augmented_mass.ncols() != self.ndofs {
             // TODO: do a resize instead of a full reallocation.
             self.augmented_mass = DMatrix::zeros(self.ndofs, self.ndofs);
@@ -1058,7 +1056,7 @@ impl Multibody {
         bodies: &RigidBodySet,
         link_id: usize,
         displacement: Option<&[Real]>,
-        mut out_jacobian: Option<&mut Jacobian<Real>>,
+        out_jacobian: Option<&mut Jacobian<Real>>,
     ) -> Isometry<Real> {
         let branch = self.kinematic_branch(link_id);
         self.forward_kinematics_single_branch(bodies, &branch, displacement, out_jacobian)

src/dynamics/joint/multibody_joint/multibody_joint.rs

@@ -17,6 +17,10 @@ use na::{UnitQuaternion, Vector3};
 pub struct MultibodyJoint {
     /// The joint’s description.
     pub data: GenericJoint,
+    /// Is the joint a kinematic joint?
+    ///
+    /// Kinematic joint velocities are never changed by the physics engine. This gives the user
+    /// total control over the values of their degrees of freedoms.
     pub kinematic: bool,
     pub(crate) coords: SpacialVector<Real>,
     pub(crate) joint_rot: Rotation<Real>,

src/dynamics/joint/multibody_joint/multibody_joint_set.rs

@@ -158,7 +158,6 @@ impl MultibodyJointSet {
         kinematic: bool,
         wake_up: bool,
     ) -> Option<MultibodyJointHandle> {
-        println!("Inserting kinematic: {}", kinematic);
         let link1 = self.rb2mb.get(body1.0).copied().unwrap_or_else(|| {
             let mb_handle = self.multibodies.insert(Multibody::with_root(body1, true));
             MultibodyLinkId {