A 4 by 4 matrix of floats, used primarily for the transformation matrix of Displayable and DisplayDevice objects. Along with general routines to rotate, translate, and scale the matrix, this also contains overloaded operators for = (copy, either a matrix or a scalar), *= (multiply, by either a matrix or a scalar), and += (add a matrix).
There are many functions in this class to simply add or multiply the matrix, to take the inverse of the matrix, or to apply rotations, translations, etc. Most importantly, functions exist to take a 3- or 4-vector, and multiply (transform) it by this matrix.