On 6/2/2015 2:32 PM, Tomasz Wlostowski wrote: > On 01.06.2015 19:09, jp charras wrote: >> Le 01/06/2015 18:23, Tomasz Wlostowski a écrit : >>> Hi all, >>> >>> I did a small investigation of the polygon-related >>> segfaults/miscalculations. It looks like Boost.polygon badly handles >>> cases where intersection points of the edges of the polygons lie close >>> to each other or overlap, causing the 'snap rounding' algorithm used in >>> boost to go haywire. This is the case for complex zones, with a lot of >>> thermal holes or via patterns (i.e. a thermal pad under a QFN with a via >>> field). >>> >>> See last comment from https://svn.boost.org/trac/boost/ticket/10642. >>> >>> There's a variety of effects I observed. >>> - a segfault. >>> - an incorrect or empty resulting polygon: merging the holes before >>> subtraction from the main outline (polyset_holes in >>> AddClearanceAreasPolygonsToPolysList) using boost::assign or subtracting >>> the holes one-by-one (instead of the whole set) fixes the segfault, but >>> I know at least one case where the resulting zone is incorrectly >>> calculated. I'll attach the test cases to the bug report on Launchpad >>> later in the evening. >> >> I am not sure subtracting the holes one-by-one (instead of the whole >> set) fixes the segfault. Because the segfault depends on the geometry, >> it does not happen when you changes the calculations for a given case, >> but can happen in an other case which previously did not crash. >> >>> >>> For the reasons above, I would strongly consider dropping >>> boost::polygon. There are also non-technical issues: >>> - It hasn't been maintained for ~1.5 years. The last activity of the >>> official maintainer was 3 years ago. >>> - the code is a mess (look at example below). >>> >>> >>> >>> @Jean Pierre: do you think Clipper is stable enough for our use? (at >>> least in case of a bug, it's actively developed and the author offers >>> support). I'm not asking about speed, it's not important if Kicad >>> crashes or produces incorrect polygons. >>> >>> Tom >> >> I don't think we can easily replace boost::polygon by Clipper. >> >> They have complementary features, but neither boost::polygon nor Clipper >> have all features we need ( for instance transform a self intersecting >> polygon into a set of not intersection polygons is easy with clipper, >> not with boost::polygon). >> >> A major issue (or lack of feature) is the fact Clipper does not handle >> holes inside a polygon by connecting holes by overlapping segments >> (to create only one polygon), which is needed in draw (and some other) >> functions > > Hi, > > I'm almost done with SHAPE_POLY_SET class for the geometry library, a > Clipper wrapper adding some missing Clipper features needed in Kicad > (e.g. polygon fracturing). I'll send a patch soon (affecting only > AddClearanceAreasPolygonsToPolysList), so that we can compare how well > it performs wrs to Boost.Polygon. > > Cheers, > Tom
Great work Tom. Thanks. Wayne >> >> I also tried to use Clipper to replace the polygon set subtracting which >> crashes Pcbnew. >> >> But if Clipper gives good results to subtract 2 polygons, this is not >> the case to subtract 2 set of polygons (when polygons inside each set >> overlap, the result is strange, whatever the settings used in calculations). >> >> Therefore, replacing boost::polygon by clipper is not trivial. >> >> If we drop boost::polygon (due to this bug, and the lack of >> maintenance), one can consider Clipper (which looks stable enough now) >> but also CGAL. >> Clipper needs not trivial rework to calculate the zone filling. >> I do not have used CGAL, but it is a large geometry library, actively >> maintained, and it could be considered before taking a decision. >> > > > _______________________________________________ > Mailing list: https://launchpad.net/~kicad-developers > Post to : [email protected] > Unsubscribe : https://launchpad.net/~kicad-developers > More help : https://help.launchpad.net/ListHelp > _______________________________________________ Mailing list: https://launchpad.net/~kicad-developers Post to : [email protected] Unsubscribe : https://launchpad.net/~kicad-developers More help : https://help.launchpad.net/ListHelp
