Intro to OpenSCAD
OpenSCAD is Open source software for creating Solid 3D CAD objects. While not the primary focus, closed 2D shapes can also be created.
Where to Get It
Links to downloadable binaries and source repositories can be found under the Download Releases section of the main OpenSCAD web page.
Primitive 2D Shapes
square(), circle(), polygon()
Primitive 3D Shapes
cube(), sphere(), cylinder(), polyhedron()