Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!julius.cs.uiuc.edu!ux1.cso.uiuc.edu!yoyodyne!marcc
From: marcc@yoyodyne.ncsa.uiuc.edu (Marc Cooper)
Newsgroups: comp.graphics
Subject: Re: Distance from Point to a Polygon? (Algorithm wanted)
Keywords: polygon point distance
Message-ID: <1991Jan4.191630.12650@ux1.cso.uiuc.edu>
Date: 4 Jan 91 19:16:30 GMT
References: <1991Jan4.131532.3933@jarvis.csri.toronto.edu>
Sender: news@ux1.cso.uiuc.edu (News)
Organization: National Center for Supercomputing Applications at Urbana Illinois
Lines: 29

In article <1991Jan4.131532.3933@jarvis.csri.toronto.edu> corkum@csri.toronto.edu (Brent Thomas Corkum) writes:
>
>
>I'm looking for a FAST algorithm for calculating the distance from a
>point in 3 space to a polygon (not the plane of the polygon) in 3 space.
>It only need work for convex three noded triangles and four noded
>quadralaterals.
>corkum@boulder.civ.toronto.edu

This seems easy enough, given the simplied case.  

First, calculate the distance from the point to the polygonal plane.  If the
intersection point is within the polygon, stop.  That is the shortest distance.

If the perpendicular dropped from the point to the polygonal plane lies OUTSIDE
the polygon, calculate the distance from each vertex of the polygon to the
point.  Then find the minimum distance between the point and the line segment
defined by the two closest vertecies.

I don't know how fast this would be.  I suppose that depends if you're willing
to hack out the calculations in the relevent assembley language or not..

-- 
Marc Cooper		| "In my childhood, I WAS an imaginary playmate."
marcc@ncsa.uiuc.edu	|	-Tom Robbins, EVEN GOWGIRLS GET THE BLUES

		National Center for Supercomputing Applications

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