Look at attached picture. There are 2 polygons. Side of first polygon
lies on side of second. What GGL will do if I unite them? Will it produce 1 polygon or 2 polygons? In other words, does it support fuzzy detection polygons with touching side. When touch side is not vertical or horizontal and they don't have same corners (e.g. they only touch by sides). _______________________________________________ ggl mailing list [hidden email] http://lists.osgeo.org/mailman/listinfo/ggl fuzzy_union.png (40K) Download Attachment |
Hi Denis,
Op 11-2-2011 4:58, Denis Pesotsky schreef: > Look at attached picture. There are 2 polygons. Side of first polygon > lies on side of second. What GGL will do if I unite them? Will it > produce 1 polygon or 2 polygons? It will produce 1 polygon. > In other words, does it support fuzzy detection polygons with touching > side. When touch side is not vertical or horizontal and they don't > have same corners (e.g. they only touch by sides). Yes, it unites polygons with touching sides. Horizontal or vertical does not matter here, and neither does having the same corners. Actually I don't call this "fuzzy detection", I mean, they must really touch. If they are just close, the two polygons will stay separate. Regards, Barend _______________________________________________ ggl mailing list [hidden email] http://lists.osgeo.org/mailman/listinfo/ggl |
Thanks for answer. But I mean a bit other thing. You noticied same
thing in your blog ("Precision, the cause of spikes"). For example, 1st polygon have coordinates like (1, 1) and (4, 2.3) (and 1 more coordinate somewhere) and other have coordinates like (2.1, y1) and (3, y2), where y1 is y coordinate for crosspoint of Line({1, 1} {4, 2.3}) and y=2.1, while y2 is y coordinate for cross-point of same line and y=3. In float-point presentation that points can be not exactly on this line, but very close. Can this result in leaving 2 separate polygons after union? 2011/2/11 Barend Gehrels <[hidden email]>: > Hi Denis, > > > Op 11-2-2011 4:58, Denis Pesotsky schreef: >> >> Look at attached picture. There are 2 polygons. Side of first polygon >> lies on side of second. What GGL will do if I unite them? Will it >> produce 1 polygon or 2 polygons? > > It will produce 1 polygon. > >> In other words, does it support fuzzy detection polygons with touching >> side. When touch side is not vertical or horizontal and they don't >> have same corners (e.g. they only touch by sides). > > Yes, it unites polygons with touching sides. Horizontal or vertical does not > matter here, and neither does having the same corners. Actually I don't call > this "fuzzy detection", I mean, they must really touch. If they are just > close, the two polygons will stay separate. > > Regards, Barend > > _______________________________________________ > ggl mailing list > [hidden email] > http://lists.osgeo.org/mailman/listinfo/ggl > ggl mailing list [hidden email] http://lists.osgeo.org/mailman/listinfo/ggl |
Op 11-2-2011 11:19, Denis Pesotsky schreef:
> Thanks for answer. But I mean a bit other thing. You noticied same > thing in your blog ("Precision, the cause of spikes"). Sure. > For example, 1st polygon have coordinates like (1, 1) and (4, 2.3) > (and 1 more coordinate somewhere) and other have coordinates like > (2.1, y1) and (3, y2), where y1 is y coordinate for crosspoint of > Line({1, 1} {4, 2.3}) and y=2.1, while y2 is y coordinate for > cross-point of same line and y=3. In float-point presentation that > points can be not exactly on this line, but very close. Can this > result in leaving 2 separate polygons after union? > In this described case, probably not, using float or double. But it might occur, yes. There is no fuzzy detection indeed. I'll come back to this with some details. Barend _______________________________________________ ggl mailing list [hidden email] http://lists.osgeo.org/mailman/listinfo/ggl |
Is there any chance that there will appear function to fix this stuff
in near future? I don't mean fuzzy detection when doing stuff. I mean something like spikes detection (that you mentioned in your blog) after doing stuff. I can list all possible cases on picture, if you want. 2011/2/11 Barend Gehrels <[hidden email]>: > Op 11-2-2011 11:19, Denis Pesotsky schreef: >> >> Thanks for answer. But I mean a bit other thing. You noticied same >> thing in your blog ("Precision, the cause of spikes"). > > Sure. >> >> For example, 1st polygon have coordinates like (1, 1) and (4, 2.3) >> (and 1 more coordinate somewhere) and other have coordinates like >> (2.1, y1) and (3, y2), where y1 is y coordinate for crosspoint of >> Line({1, 1} {4, 2.3}) and y=2.1, while y2 is y coordinate for >> cross-point of same line and y=3. In float-point presentation that >> points can be not exactly on this line, but very close. Can this >> result in leaving 2 separate polygons after union? >> > In this described case, probably not, using float or double. But it might > occur, yes. There is no fuzzy detection indeed. I'll come back to this with > some details. > > Barend > > _______________________________________________ > ggl mailing list > [hidden email] > http://lists.osgeo.org/mailman/listinfo/ggl > ggl mailing list [hidden email] http://lists.osgeo.org/mailman/listinfo/ggl |
Hi Denis,
On 2-3-2011 12:44, Denis Pesotsky wrote: > Is there any chance that there will appear function to fix this stuff > in near future? I don't mean fuzzy detection when doing stuff. I mean > something like spikes detection (that you mentioned in your blog) > after doing stuff. I can list all possible cases on picture, if you > want. Yes, there is also a remark at my blog about this. I will come with the details, but if you have pictures or preferably WKT-representations, that would help me to check if the solution is applicable in all cases. Thanks, Barend -- Barend Gehrels http://about.me/barendgehrels _______________________________________________ ggl mailing list [hidden email] http://lists.osgeo.org/mailman/listinfo/ggl |
In one or two days I'll hack my CAD-like app to use GGL for polygons
union and subtractions, so it will be easy to test stuff. Will send message here, when I will do that. Thanks. 2011/3/6 Barend Gehrels <[hidden email]>: > Hi Denis, > > On 2-3-2011 12:44, Denis Pesotsky wrote: >> >> Is there any chance that there will appear function to fix this stuff >> in near future? I don't mean fuzzy detection when doing stuff. I mean >> something like spikes detection (that you mentioned in your blog) >> after doing stuff. I can list all possible cases on picture, if you >> want. > > Yes, there is also a remark at my blog about this. I will come with the > details, but if you have pictures or preferably WKT-representations, that > would help me to check if the solution is applicable in all cases. > > Thanks, Barend > > -- > Barend Gehrels > http://about.me/barendgehrels > > _______________________________________________ > ggl mailing list > [hidden email] > http://lists.osgeo.org/mailman/listinfo/ggl > ggl mailing list [hidden email] http://lists.osgeo.org/mailman/listinfo/ggl |
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