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From: bcphyagi@csunb.csun.edu (Stephen Walton)
Newsgroups: comp.sys.amiga.advocacy
Subject: Re: Contour plotting
Message-ID: <1991Mar1.213257.6960@csun.edu>
Date: 1 Mar 91 21:32:57 GMT
References: <1991Feb27.194218.12227@csun.edu> <1991Feb28.173901.27728@bilver.uucp>
Sender: news@csun.edu (News Administrator)
Organization: csun
Lines: 49

In article <1991Feb28.173901.27728@bilver.uucp> alex@bilver.uucp (Alex
Matulich) writes:

>Comparing two machines according to completely different contour algorithms
>tells nobody anything.

It does if the two algorithms purport to accomplish the same thing--it
tells you how long it will take each machine to perform the task I
require. 

>If you are only going to display your contour plots on a video screen,
>there are a LOT of things you can do to speed up the algorithm.

PLPLOT is not in this category.  It supports the Amiga screen,
Tektronix terminals, HP Laser Jet II and Postscript printers, and HP
7451 pen plotters.  Besides, I was in fact comparing the relative times
required to get screen plots. 

You also missed the point that this two-hour+ operation to generate the
contours in GRAFTOOL is *required before* you can get the pen plot.
PLPLOT will generate the pen plot directly. 

>For the pen-plotter algorithm, you have to design the routine to minimize
>the number of pen lifts and pen color changes.

PLPLOT uses an algorithm like this.  If you watch it run on the Amiga
screen, it does in fact produce one contour interval at a time, making
a complete pass through the data for each contour level.  I admit that
I've never tried the pen plot part, but I bet it takes much less than
the time GRAFTOOL takes to just do the screen version. 

>I would venture that the GRAFTOOLS algorithm would take just as long if
>it were run on the Amiga.

I can easily believe this :-) .

>And your Amiga PLPLOT library would probably run in as short a time if
>it were ported to MSDOS.

Please tell me how to run the following loop under MSDOS:

        float **z;

	z = (float **) malloc(512 * sizeof(float *));
	for (i = 0; i < 512; i++)
		z[i] = (float *) malloc(512 * sizeof(float));
--
Stephen R. Walton, Dept. of Physics and Astronomy, Cal State Northridge
bcphyagi@csunb.csun.edu until my Suns come back up