## Tuesday, May 29, 2012

### Python Constructive Solid Geometry

As mention in a previous post, I've started work on a Constructive Solid Geometry (CSG) library. The library is currently written in C++ and uses Carve to do the heavy lifting. I am also planning a CGAL back-end since so far, it seems more robust than Carve to geometric degeneracies. Unfortunately, lack of strict compliance to the IEE754 spec by the LLVM and Clang compilers means that I can't develop and test this under OS-X 10.7, my primary development machine.

The ultimate goal is a simple, easy to use library with functionality akin to OpenSCAD, but usable from mainstream languages (C++ and Python). I currently have a basic implementation functional, including mesh loading and saving (.OFF, .OBJ and .STL), affine transformations, basic primitives and CSG operations union, difference, symmetric difference, and intersection. All of this functionality is available through python via a BOOST.python wrapper.

Here's a sample python script, generating a weird table thing:
from pyCSG import *

table = polyhedron()
table_top = polyhedron()
table_leg = polyhedron()

table_top.make_box( 1.0, 1.0, 1.0, True )
table_leg.make_sphere( 0.5, True )

table = table_top.scale( 4.0, 0.25, 3.0 )
table = table.union( table_leg.translate(-1.5,-0.4,-1.0 ) )
table = table.union( table_leg.translate( 1.5,-0.4,-1.0 ) )
table = table.union( table_leg.translate( 1.5,-0.4, 1.0 ) )
table = table.union( table_leg.translate(-1.5,-0.4, 1.0 ) )

torus = polyhedron();
torus.make_torus( 1.0, 0.25, True )
table = table.difference( torus.translate( 0.0, 0.25, 0.0 ) )

table.save_mesh("table.obj");

Which produces the output (viewed in MeshLab):

Note that this is a single watertight mesh suitable for 3D printing, machining or meshing for finite element analysis.  I'm still finalizing the API, but will release the code when it's a bit more stable which I hope will make parametric design and optimization much more practical with open source tools.

#### 1 comment:

rajput said...
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