PyOpenSCAD/ SolidPython                                             8 Mar 2011

    PyOpenSCAD is a generalization of Phillip Tiefenbacher's openscad module, 
found at http://www.thingiverse.com/thing:1481.  It generates valid OpenSCAD 
code from Python code with minimal overhead.  Here's a simple example:
    
This Python code: 

from pyopenscad import *
d = difference()(
    cube(10),
    sphere(15)
)
print scad_render( d)

Generates this OpenSCAD code:

difference(){
	cube(10);
	sphere(15);
}

Steps to using PyOpenSCAD
------------------------------
-  from pyopenscad import *
-  call 'use( "/path/to/scadfile.scad")' or 'include("/path/to/scadfile.scad")' 
    for any included SCAD code
-  OpenSCAD uses curly-brace blocks ({}) to create its tree.  PyOpenSCAD uses
    parentheses with comma-delimited lists.
    -  Ex:  OpenSCAD:
        -  difference(){
              	cube(10);
              	sphere(15);
              }
    -  PyOpenSCAD:
        -  d = difference()(
                    cube(10),  # Note the comma between each element!
                    sphere(15)
                )
           
-  Call scad_render( py_scad_obj)   to generate SCAD code. This returns a string 
    of valid OpenSCAD code.
-  OR:  call  scad_render_to_file( py_scad_obj, filepath) to
      store that code in a file. 
    -  If 'filepath' is open in the OpenSCAD IDE and Design =>
          'Automatic Reload and Compile' is checked, calling
          scad_render_to_file() from Python will load the object in
          the IDE.
    -  Alternately, you could call OpenSCAD's command line and render straight 
        to STL.   

Extra syntactic sugar
------------------------------
-   Following Elmo Mäntynen's suggestion, SCAD objects override 
    the basic operators + (union), - (difference), and * (intersection).
    So:
        c = cylinder( r=10, h=5) + cylinder( r=2, h=30) 
    is the same as:
        c = union()(
                cylinder( r=10, h=5),
                cylinder( r=2, h=30)
            )
    Likewise:
        c = cylinder( r=10, h=5)
        c -= cylinder( r=2, h=30)
    is the same as:
        c = difference()(
                cylinder( r=10, h=5),
                cylinder( r=2, h=30)
            )

SP_utils
------------------------------
I've been adding utilities to sp_utils.py.  Currently these include:
-- Basic color library:  I took this from someone on Thingiverse and I'm 
    ashamed that I can't find the original source.  I owe someone some 
    attribution.
    
-- Directions: (up, down, left, right, forward, back) for arranging things:
        up(10)(
            cylinder()
        )
    seems a lot clearer to me than:
        transform( [0,0,10])(
            cylinder()
        )
    
    Again, I took this from someone's SCAD work and have lost track of the 
    original author.  My apologies.
    
-- Arcs: I've found this useful for fillets and rounds.
        arc( rad=10, 90, 210) 
    draws an arc of radius 10 counterclockwise from 90 to 210 degrees. 
    
    Also: 
        arc( rad=10, 0, 90, invert=True ) 
    draws the portion of a 10x10 square NOT in a 90 degree circle of radius 10.
    This is the shape you need to add to make fillets or remove to make rounds.
    
    
-- Bill Of Materials:  Put '@part()' before any method that defines a part, then 
    call bill_of_materials() after the program is run, and all parts will be 
    counted, priced and reported. Check it out.
    

Advantages
------------------------------
Because you're using Python, a lot of things are easy that would be hard or 
impossible in pure OpenSCAD.  Among these are:
-- recursion
-- built-in dictionary types
-- mutable, slice-able list and string types
-- external libraries (images! 3D geometry!  web-scraping! ...)

Enjoy, and please send any questions or bug reports to me at evan_t_jones@mac.com. Cheers!
Evan