cae-tools/poly2d

poly2d - Yet another 2D polygon library
=======================================

Why do we need another 2D polygon library, if there are already CGAL,
Boost, Clipper, GPC, ... ?

All the above are either written in a weird language, are under a
non-Free license, or simply don't provide the feature set we need
here. poly2d is written in C, doesn't depend on non-standard
libraries, and is licensed under the GPL (will change to LGPL).

poly2d serves itself liberally from code already in cameo but
provides a simpler and cleaner interface. The first objective is
to provide the tools to replace the (badly broken) area filling
operation in cameo. Later, poly2d could replace more parts of
cameo.

poly2d puts more emphasis on simplicity than on performance. Some
functions expect clockwise closed polygons that don't self-intersect.
The table below shows the capabilities

Open     Counter-clockwise
|  Concave  Min. vertices
|  |  Self-intersect
|  |  |  |  |
Y  Y  Y  Y  0		p2d_contains_poly(b), p2d_free, p2d_free_all,
			p2d_is_closed, p2d_copy, p2d_reverse, p2d_vertices,
			p2d_write_gnuplog, p2d_write_gnuplot_all
Y  Y  Y  Y  1		p2d_read_gnuplot
-  Y  Y  Y  0		p2d_simplify
-  Y  -  Y  3		p2d_is_cw
-  Y  -  -  3		p2d_contains_point, p2d_contains_poly (a),
-  Y  -  #  3		p2d_area*, p2d_offset*

# CGAL uses ccw, poly2d uses cw. Need to switch.

Not yet implemented:
- p2d_simplify (low priority - the offsetting from CGAL already covers
  the main use case)

Not yet specified:
- subtraction (do we actually need it ?)

Other:
- change the license from GPL to LGPL
- change ccw to cw
- make sure CGAL is only fed ccw ploygons and cw holes
- transform CGAL's idea of outer polygons into something we can use
- use more meaningful offset/overlap model for area fill
- check for memory leaks
- try to generate dependencies also for *.cpp

Prerequisite:
libcgal-dev