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Re: POLYFILLV weirdness [message #51402 is a reply to message #51350]

Mon, 20 November 2006 14:49

badjelly.witch
Messages: 27
Registered: May 2006

Junior Member

I second JD's response. There are many routines in IDL that are
disturbingly vague about where the pixel edges and pixel centres lie.
Perhaps this is because of IDL's emphasis on image processing, where
the number of pixels is large and the edge effects don't matter (much).

A few years ago I wrote a reasonably versatile--but not very
fast--pollyfillv-replacement routine using Sutherland-Hodgman clipping
code I got from JD. (I think the problem I was addressing at the time
was to calculate the land fraction for each cell in an ocean-model grid
given coastline information.) Just the other day I had to revive this
stuff and after 20 minutes of intense mental anguish I established that
it works as it should and on a modern computer it's acceptably fast.
The routine handles arbitray polygons projected onto rectilinear or
curvilinear 2D grids. I'm happy to give you a copy, or you might want
to try JD's implementation.

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[Message index]

		POLYFILLV weirdness By: dktr.ted on Thu, 16 November 2006 19:29
		Re: POLYFILLV weirdness By: badjelly.witch on Mon, 20 November 2006 14:49
		Re: POLYFILLV weirdness By: JD Smith on Mon, 20 November 2006 12:31
		Re: POLYFILLV weirdness By: Jean H. on Sun, 19 November 2006 14:43
		Re: POLYFILLV weirdness By: dktr.ted on Fri, 17 November 2006 15:52

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