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cae-tools/poly2d
Werner Almesberger 53fe70950d poly2d/: try to work around spurious aborts in CGAL::create_interior_skeleton_and_offset_polygons_with_holes_2
cameo encountered spurious aborts with the following message:

  terminate called after throwing an instance of 'CGAL::Precondition_exception
  what():  CGAL ERROR: precondition violation!
  Expr: is_simple_2(first, last, traits)
  File: /usr/include/CGAL/Polygon_2/Polygon_2_algorithms_impl.h
  Line: 420

These aborts come and go even if just the coordinate origin is slightly
changed. Setting CGAL_POLYGON_NO_PRECONDITIONS in p2d_area_holes.cpp
made them go away in some cases, but cameo could still run into an
assertion violation (in CGAL).

We now check all the polygons, outer boundary and holes, being sent to
CGAL::create_interior_skeleton_and_offset_polygons_with_holes_2 for
simplicity, and stop recursing if there is any hint of a problem.

This seems to avoid trouble for now, but the issue deserves further
investigation.
2012-08-22 13:50:19 -03:00
..
test poly2d/: add foreach_v2d* and foreach_edges looping constructs 2012-05-08 14:06:00 -03:00
cgal_helper.h poly2d/: automatically switch between clockwise and counter-clockwise polygons 2012-05-07 22:12:21 -03:00
Makefile poly2d/: add foreach_v2d* and foreach_edges looping constructs 2012-05-08 14:06:00 -03:00
p2d_area_holes.cpp poly2d/: try to work around spurious aborts in CGAL::create_interior_skeleton_and_offset_polygons_with_holes_2 2012-08-22 13:50:19 -03:00
p2d_area.c poly2d/: simplify semantics of first/next offset in area fill 2012-05-07 22:45:39 -03:00
p2d_attrib.c poly2d/: Yet another 2D polygon library (WIP) 2012-05-06 23:51:38 -03:00
p2d_contains_point.c poly2d/: Yet another 2D polygon library (WIP) 2012-05-06 23:51:38 -03:00
p2d_contains_poly.c poly2d/: Yet another 2D polygon library (WIP) 2012-05-06 23:51:38 -03:00
p2d_copy.c poly2d/: Yet another 2D polygon library (WIP) 2012-05-06 23:51:38 -03:00
p2d_free.c poly2d/: Yet another 2D polygon library (WIP) 2012-05-06 23:51:38 -03:00
p2d_gnuplot.c poly2d/: Yet another 2D polygon library (WIP) 2012-05-06 23:51:38 -03:00
p2d_hsort.c poly2d/p2d_hsort.c (p2d_hier_free): use p2d_free, not p2d_free_all 2012-05-08 00:51:43 -03:00
p2d_hsort.h poly2d/: Yet another 2D polygon library (WIP) 2012-05-06 23:51:38 -03:00
p2d_make.c poly2d/: Yet another 2D polygon library (WIP) 2012-05-06 23:51:38 -03:00
p2d_offset.cpp poly2d/: automatically switch between clockwise and counter-clockwise polygons 2012-05-07 22:12:21 -03:00
poly2d.h poly2d/: add foreach_v2d* and foreach_edges looping constructs 2012-05-08 14:06:00 -03:00
README poly2h/: auto-generate dependencies also for C++ code 2012-05-07 22:53:45 -03:00
util.h poly2d/: Yet another 2D polygon library (WIP) 2012-05-06 23:51:38 -03:00
v2d_intersect.c poly2d/: Yet another 2D polygon library (WIP) 2012-05-06 23:51:38 -03:00
v2d_line_distance.c poly2d/: Yet another 2D polygon library (WIP) 2012-05-06 23:51:38 -03:00

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 closed polygons that don't self-intersect. For now,
it doesn't matter whether polygons are clockwise or counter-clockwise. 
The table below shows the capabilities

Open     Min. vertices
|  Concave
|  |  Self-intersect
|  |  |  |
Y  Y  Y  0		p2d_contains_poly(b), p2d_copy, p2d_free, p2d_free_all,
			p2d_is_closed, p2d_no_intersect, p2d_reverse,
			p2d_vertices, p2d_write_gnuplot, p2d_write_gnuplot_all
Y  Y  Y  1		p2d_read_gnuplot
-  Y  Y  0		p2d_simplify
-  Y  -  3		p2d_is_cw
-  Y  -  3		p2d_contains_point, p2d_contains_poly (a),
-  Y  -  3		p2d_area*, p2d_offset*

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
- transform CGAL's idea of outer polygons into something we can use
- check for memory leaks

Prerequisite:
libcgal-dev