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Is there a way to get outer points of selected polygons?

kbhow

Hi,

Is there any SKILL codes which able to get the outer points of selected objects?

I was trying to create a new function which may required to get the outer points of selected objects (polygon/rectangle/instances and etc). I want to get a list of points where i can use it to create a polygon which cover all selected objects.

Example, let say i have selected 10 polygons, and i want a function to return me a list of outer points of my selected object. Can someone help?

Thanks

How

Parents

  • To be slightly pedantic, even if it is effectively one shape, it's possible that the dbLayer functions may return more than one shape if there are too many points.

    There's an optional argument to dbLayer* functions which specifies the maximum number of vertices - and the default is (I think, if my memory is correct) 200. Beyond that it automatically splits into pieces. This was done because some formats historically have limits on the number of vertices (e.g. stream format had a historical limit of 200 points per polygon).

    So counting the number of shapes produced may not be sufficient to detect gaps if there are lots of vertices in the resulting shape (if it has an outline like the coast of Norway ;-> ). That said, I believe that the upper limit is enormous (not even sure there is an upper limit) in OA versions is very high; in CDB the upper limit of number of vertices per polygon is 4000 (I think). So you may be able to use Stefan's approach still if you have a relatively small set of data to find the "hull" for.

    Regards,

    Andrew.

     

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  • To be slightly pedantic, even if it is effectively one shape, it's possible that the dbLayer functions may return more than one shape if there are too many points.

    There's an optional argument to dbLayer* functions which specifies the maximum number of vertices - and the default is (I think, if my memory is correct) 200. Beyond that it automatically splits into pieces. This was done because some formats historically have limits on the number of vertices (e.g. stream format had a historical limit of 200 points per polygon).

    So counting the number of shapes produced may not be sufficient to detect gaps if there are lots of vertices in the resulting shape (if it has an outline like the coast of Norway ;-> ). That said, I believe that the upper limit is enormous (not even sure there is an upper limit) in OA versions is very high; in CDB the upper limit of number of vertices per polygon is 4000 (I think). So you may be able to use Stefan's approach still if you have a relatively small set of data to find the "hull" for.

    Regards,

    Andrew.

     

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