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From: kent@swrinde.nde.swri.edu (Kent D. Polk)
Newsgroups: comp.sys.amiga.advocacy
Subject: Re: Contour plotting
Message-ID: <1673@swrinde.nde.swri.edu>
Date: 1 Mar 91 15:14:06 GMT
References: <1991Feb27.194218.12227@csun.edu> <1991Feb28.173901.27728@bilver.uucp>
Sender: news@swrinde.nde.swri.edu
Organization: Southwest Research Institute, San Antonio, Texas
Lines: 61

In article <1991Feb28.173901.27728@bilver.uucp> alex@bilver.uucp (Alex Matulich) writes:
>In article <1991Feb27.194218.12227@csun.edu> bcphyagi@csunb.csun.edu (Stephen Walton) writes:
>>Using the demo version of this "wonderful, beautiful, powerful" program
>>called GRAFTOOL for MS/DOS (which has received rave reviews) I had to:
>>1) generate a 3-d plot of the image (1 hour) and 2) ask the program to
>>generate the contour plot (another hour+, I haven't had the patience to
>>run it to completion).  This is on a _20 MHz_ 386 machine!
>>
>>To do the same thing on my good old Amiga 2000 (no FPU, 7 MHz 68000),
>>I malloc'ed a 512 by 512 float array and called Tony Richardson's
>>plcont() routine from his PLPLOT library.  Total time for generating
>>the plot was less than 5 minutes.  It is less than 1 minute on a 3000.
>
>Comparing two machines according to completely different contour algorithms
>tells nobody anything.  As a programmer who has written contour-drawing
>algorithms for different purposes, I think I can shed some light on this. 
> 
>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.  On the other hand,
>if you are going to output your contours to a pen plotter, which is what
>I think GRAFTOOL's algorithm was designed for, things slow down considerably.

I think you missed the point as well as not knowing what PLPLOT is.
First, PLPLOT is a device-independent 3D PLOTTING library for the Amiga
and Unix boxes. It supports pen plotters, which are its lowest common
denominator, postscript, tektronics, IFF, etc., so there are no
algorithms to speed up things for screens.  The screen operations on an
Amiga are simply tremendously faster, and the architecture of the
machine allows a much more straightforward approach to writing
software, and I expect this is where PLPLOT really picks up its speed,
as compared to GRAFTOOL.

I also believe Mr. Walton was comparing overall the ease with which you
can perform operations on an Amiga, regardless of how you accomplish
it, versus the MSDOS environment. If this is the case, I second his
view.  While there may not be as much 'packaged' software on the Amiga,
the PD offerings like PLPLOT and the ease with which data can be moved
from program to program on the Amiga (kind of like Unix filters :^) allow
a remarkable environment for those who don't mind a little brainwork.

>Take a careful look at the capabilities of your contouring programs on
>the Amiga and IBM compatibles.  What are they designed for?  I would
>venture that the GRAFTOOLS algorithm would take just as long if it were
>run on the Amiga.  And your Amiga PLPLOT library would probably run
>in as short a time if it were ported to MSDOS.

One of our guys looked into porting it. The severe limitations of
MS-DOS would require a tremendous effort to get around the 64k segment
limitations.  You can't even compile the PLPLOT stick fonts under
MS-DOS! From my programming experiences on both machines, I would say
that for 'similar' platforms, the MSDOS programs would run much slower;
tremendously slower when using screen graphics.

Back to PLPLOT. We use it quite a bit. While it definitely has some
limitations, it is a very capable library. Maybe some day I'll get
around to fixing some of the problems. The author has decided to not
continue further development. Anyone want to pick this up?

Kent Polk: Southwest Research Institute (512) 522-2882
Internet : kent@swrinde.nde.swri.edu
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