This shape provides a simple visualization of a wheel.
The center of the wheel is located by position
vector r. Its orientation is given by the
orientation object R, whereby wheel's spin axis
points in y direction of R and
its middle plane is in the x-z plane
of R. The wheel's rotation about its spin axis,
i.e. about axis y of R, can be
realized directly by the input psi.

The dialog variables R, r,
psi, radius, rRim,
width, color and
specularCoefficient are declared as (time varying)
input variables. If the default equation is not
appropriate, a corresponding modifier equation has to be
provided in the model where the shape instance is used.
Variable color is a RGB color space given in the range 0 .. 255. Predefined colors from Types.Defaults are used throughout the library to get a coherent visualization.