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Re: clipping with polyfill [message #29945 is a reply to message #29925]

Tue, 26 March 2002 13:56

Mark Hadfield
Messages: 783
Registered: May 1995

Senior Member

"David Fanning" <david@dfanning.com> wrote in message
news:MPG.170a8e0a84f81cef989850@news.frii.com...
> James Kuyper (kuyper@gscmail.gsfc.nasa.gov) writes:
>
>> It seems to me that this does the right thing only when the edges
>> of the polygon that are clipped are perpendicular to the clipping
>> boundary. Otherwise, it changes the orientation of those edges.
>
> Right, that's what all that replacement nonsense I wrote before was
> about. If the clipping place is not exactly on a data boundary, the
> edges of the polygon will be off and you will have to replace the
> data value with the clipping value. You will have to interpolate,
> essentially. :-)

I haven't been following this thread very closely, but are you talking
about clipping a polygon to a rectangular region? If so my
MGH_POLYCLIP might be of use. It clips a 2D polygon to a vertical or
horizontal line. Apply it four times to clip to a box. As explained in
the header, it's based on a function of JD's but I did some
performance tuning (and changed the name to annoy him). See:

http://katipo.niwa.cri.nz/~hadfield/gust/software/idl/

--
Mark Hadfield
m.hadfield@niwa.co.nz Ka puwaha et tai nei
http://katipo.niwa.co.nz/~hadfield Hoea tatou
National Institute for Water and Atmospheric Research (NIWA)

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[Message index]

		Re: clipping with polyfill By: Charlie Zender on Wed, 27 March 2002 10:24
		Re: clipping with polyfill By: Mark Hadfield on Tue, 26 March 2002 13:56
		Re: clipping with polyfill By: David Fanning on Tue, 26 March 2002 12:54
		Re: clipping with polyfill By: James Kuyper on Tue, 26 March 2002 12:44
		Re: clipping with polyfill By: David Fanning on Tue, 26 March 2002 12:11

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