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From: p_davis@epik.enet.dec.com (Peter Davis)
Newsgroups: comp.windows.x
Subject: Re: HELP: need to draw curve through points
Message-ID: <18695@shlump.nac.dec.com>
Date: 4 Jan 91 17:10:38 GMT
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In article <340@coatimundi.cs.arizona.edu>, slm@cs.arizona.edu (Sandy Miller) writes...
>I'm looking for an algorithm that will allow me to draw a smooth
>curve through a set of points input by a user.  The points may be
>anywhere within a window (i.e. not limited to increasing x values).
>Has anybody seen/done something like this?  I would appreciate any
>and all help.
>

You'll have to solve this in two parts.  First, you have to find a smooth curve
through (or near) the input points.  There are a number of published algorithms
for doing this.  One is Philip Schneider's, as published in _Graphics Gems_,
(ed. by Andrew Glassner, Academic Press, 1990).

The second step is to figure out how to draw curves in X, since X doesn't have
curve drawing operations.  You basically have to approximate the curve by a
polygon, and draw the individual line segments.  Again, there are a number of
published techniques for doing this.  You could check "the Bible": _Computer
Graphics: Principles and Practice_ by Foley, van Dam, Feiner, and Hughes
(Addison Wesley, 1990).  There's also a book around called something like
_Constructing Computer Graphics Software_ which has a pretty good, simple
algorithm.  I forget the author and publisher, but you should be able to find
it.

-pd