polygon resize() generates bad/broken vertices

[Andy Ross <andy@…>]

boost::polygon::resize() (and its variants: shrink()/bloat()/operator+(), etc...) routinely produces "bad" vertices in the output stream. Most of the shrunken polygon is correct, but a handful of vertices seem to be replaced with visually random locations.

The attached code (which has non-trivial input data, but not so complicated that it can't be inspected by hand) shows the problem pretty clearly. The "before" polygon (image attached) looks good, the "after" shrunken version is mostly correct with some oddball excursions.

Setting corner_fill_arc to true suppresses this behavior, and the output polygon looks more correct (though obviously the output is different). That, however, has some severe performance problems (to be detailed in a separate bug) and isn't an acceptable substitute.

This is a showstopper for me right now. Test vs. svn as of submission date.

[Andy Ross <andy@…>]

Code to exercise bug (and also generate attached images)

[Andy Ross <andy@…>]

pre-shrink polygon

[Andy Ross <andy@…>]

post-shrink polygon, with bad vertices

[Lucanus Simonson]

Very small features before shrinking can become very large after if the angle is accute. That is what happened in this case.