mention some additional joints

Author: baggepinnen

docs/src/index.md

@@ -179,7 +179,7 @@ Pages   = ["frames.jl"]
 
 A joint restricts the number of degrees of freedom (DOF) of a body. For example, a free floating body has 6 DOF, but if it is attached to a [`Revolute`](@ref) joint, the joint restricts all but one rotational degree of freedom (a revolute joint acts like a hinge). Similarily, a [`Prismatic`](@ref) joint restricts all but one translational degree of freedom (a prismatic joint acts like a slider).
 
-A [`Spherical`](@ref) joints restricts all translational degrees of freedom, but allows all rotational degrees of freedom. It thus transmits no torque.
+A [`Spherical`](@ref) joints restricts all translational degrees of freedom, but allows all rotational degrees of freedom. It thus transmits no torque. A [`Planar`](@ref) joint moves in a plane, i.e., it restricts one translational DOF and two rotational DOF. A [`Universal`](@ref) joint has two rotational DOF.
 
 Some joints offer the option to add 1-dimensional components to them by providing the keyword `axisflange = true`. This allows us to add, e.g., springs, dampers, sensors, and actuators to the joint.
 

src/Multibody.jl

@@ -26,6 +26,7 @@ Create a 3D animation of a multibody system
 - `loop`: The animation will be looped this many times. Please note: looping the animation using this argument is only recommended when `display = true` for camera manipulation purposes. When the camera is not manipulated, looping the animation by other means is recommended to avoid an increase in the file size.
 - `filename` controls the name and the file type of the resulting animation
 - `traces`: An optional array of frames to show the trace of.
+- `show_axis = false`: Whether or not to show the plot axes, including background grid.
 
 # Camera control
 The following keyword arguments are available to control the camera pose: