Specifications for Three-dimensional PostScript (PreScript)
Since our interpreter is no longer a preprocessor, maybe a new name!

A three-dimensional path will be specified as a double-array in the 
form: [ [x1 y1 z1 /command1] [x2 y2 z2 /command2] ...]

where x,y, and z are point specifications for various commands and 
/command can be moveto, lineto, rmoveto, and rlineto.

3-Dimensional Path Operators
newpath3       - begins a new 3D path. Clears any current path.
reversepath3   - reverses the direction of a 3D path.
closepath3     - Makes a set of closed 2D objects from the path.
currentpoint3  - Returns the x y z coordinate of the current point
x y z moveto3  - Moves to an new x y z coordinate, starting a new subpath
x y z rmoveto3 - Moves to a new x y z delta, starting a new subpath
x y z lineto3  - Extends the path along the line to the point x y z 
x y z rlineto3 - Extends the path along the delta line x y z
pathbbox3      - Returns three points for the three opposite corners
                 of a cube bounding the path
pathforall3    - Moves through the 3D path and executes operators 
                 much like the 2D pathforall
n lastplace3   - Grabs data from a stack of last currentpoints

x y z translate3  - Translates the viewpoint by x y z deltas
x y z scale3      - Scales the viewpoint by x y z ratios

x1 y1 z1 x2 y2 z2 angle rotppa3 - Rotate based on point point angle, meaning
                                - That the two points specify a line and
                                - The angle starts at zero with a plane
                                - intersecting the origin.

[a b c d e f g h i j k l] (CTM)
matrix,initmatrix,identmatrix,defaultmatrix,currentmatrix,setmatrix,concat
concatmetrix,transform,dtransform,itransform,idtransform,invertmatrix
   - Matrix transformations

There is a new variable called "plane" represented internally as (Ax+By+Cz+D=0)
But it can be defined in several ways:
   3pts
   xyz intercepts
   point and normal
   axis and angle from origin
   old plane and translate in direction of normal
   old plane and rotate around axis
   transform old plane with matrix
Can do things in planes
Manipulate planes

Finally there is an object prism3 which takes a plane with an image
  and moves this plane to a new 3D location, and then does a one-to-one
  mapping of all vertices in the two drawings, connecting the lines
  and the quadrilaterals the lines forms, so that the lines can be stroked
  or can be filled in.

Somehow handling of 3D volumetric filling and clipping?
Somehow handling of 3D opaqueness so that objects "behind" have
   their line segments either entirely or partially hidden?