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Info-Graphics Digest	Sun Jun 14 03:00:35 PDT 1987

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Today's Topics:

 Drawing Contour Maps
 Ray Tracing
  Raster Technologies One/380
 Lecture in San Francisco 18-Jun-87: HISTORY OF COMPUTER GRAPHICS
 Survey: Microcomputers in Graphics Education
 Contour plots [C PROGRAM SOURCE]

----------------------------------------------------------------------

Date:     8 Jun 1987 15:19:10-WET
From: malcolm <MALCOLM%UK.AC.PCL.LYNX@AC.UK>

  Hello ,

   Does anyone out there know of the existence of a Tekronix
   4010 emulator for a PC compatible. It must be public domain,
   I have seen a few around and tried them out, but they don't seem
   to like my PC, an OPUS II with CGA card in it.

    Thankyoueversomuch,

        Malcolm John Taylor
        Polytechnic of Central London
        115 New Cavendish St London W1M 8JS


       Try these addresses :-
       malcolm%uk.ac.pcl.lynx@ukacrl.bitnet       BITNET
       malcolm%ib.rl.ac.uk                        EARN
       malcolm%uk.ac.pcl.lynx@cs.ucl.ac.uk        ARPA
       mcvax!ukc!uk.ac.pcl.lynx!malcolm           UUCP



------------------------------

Date: Mon, 8 Jun 87 20:19:27 ADT
From: Kevin Marinelli <dalcs!marinell@seismo.CSS.GOV>
Subject: Drawing Contour Maps
Organization: Dept. of Math., Stats & C.S., Dalhousie University, Halifax, N.S., Canada

   This is not an optimal solution, but...

   The last issue of BYTE has a set of BASIC subroutines for drawing
   contour maps on a PC. This program shouls be easily modified to 
   meet your needs.

   If this does not work, let me know, and I will dig up some FORTRAN
   source code and mail it to you. 

   The point is, try it first from the BASIC to see how it works. That
   way you will learn the many limitations of using computers to contour
   data. (i.e.  contour maps drawn by a computer are not gospel. It follows
   the GIGO principle very closely).

   Kevin Marinelli
   Academic Computing Services
   Dalhousie University


------------------------------

Date: Tue, 9 Jun 87 15:13:34 CDT
From: Kent Michael White <kmw%usl.csnet@RELAY.CS.NET>
Subject: Ray Tracing

The Center For Advanced Computer Studies at the University
of Southwestern Louisiana presently has a small research group
that is interested in ray tracing algorithms. We are wanting
to confer with other research groups concerning new ray tracing
techniques.
Please respond directly to me kmw@usl.usl.edu since I do not
currently receive mod.graphics.


------------------------------

Date: Tue, 19 May 87 08:47 EDT
From: <BEGEMAN%MCOIARC.BITNET@wiscvm.wisc.edu>
Subject:  Raster Technologies One/380


We have just recieved the 87 edition of Movie.byu with the interface to the
Raster Tech one/20.  That's all fine and dandy, but we have a Raster Tech
One/380.  Does anyone out there have an interface to the Raster Tech one/380
for movie.byu that they would be willing to share?  We currently have the
One/380 connected DMA to a VMS  VAX 11/780.

                                Mike Begeman
                                Medical College of Ohio
                                <begeman@mcoiarc>

------------------------------

Date: Tue, 9 Jun 87 17:46:19 PDT
From: Info-Graphics-Request@ADS.arpa (Andy Cromarty)
Subject: Lecture in San Francisco 18-Jun-87: HISTORY OF COMPUTER GRAPHICS

 From siggraph@ames-pioneer.arpa Fri Jun  5 15:59:41 1987
 Path: ads!siggraph
 From: siggraph@ames-pioneer.arpa
 Subject: 6/18 6PM Joint Golden Gate/BA ACM/SIGGRAPH Chapters, Hist. of CG
 Message-ID: <28392@ads.ARPA>
 Date: 5 Jun 87 22:59:41 GMT
 Sender: daemon@ads.ARPA
 Lines: 40
 Status: RO
 
 From: Siggraph <siggraph@ames-pioneer.arpa>
 
 Joint Golden Gate Chapter ACM and Bay Area ACM/SIGGRAPH
 
                   HISTORY OF COMPUTER GRAPHICS
                      A Biased Personal View
 
                          Alvy Ray Smith
                          Vice President
                               Pixar
 
 Thursday June 18
 
 Exploratorium, McBean Theater
 3601 Lyon Street, SF
 
 
 6:00..7:00	Cocktails and Hors D'oeuvres
 7:00..8:00	Speaker & Q/A
 
 Please call (415)-339-3024 by June 11 if you would like to make
 reservations (recommended) for hors d'oeuvres ($10).
 
 
 ABSTRACT - The dark ages of black-and-white lines at NYU. How
 the University of Utah did it with no equipment. How Xerox PARC
 kissed off color graphics but got an Emmy anyway. How Alex
 Schure met Ivan Sutherland and begat NYIT. How Evans & Sutherland
 succeeded & failed. How Siggraph grew up. The sad story of
 standards. The amazing stories of NYIT: Los Ricos National
 Forest, "make Tubby dance", Holloway house. Who said, "Our goal
 is to speed up time, eventually deleting it"? David Em unmasked
 (the M is revealed). Jim Blinn dances. Video art vs computer
 graphics. How Lucasfilm happened. Star Trek. Star Wars. Ravi
 Shankar. Steven Spielberg. Sylvester Stallone. Special effects.
 Do you remember III, DP, Abel, Omnibus, Digital Effects,
 MAGI? What Pixar means. How it feels to spin off. Luxo Lamps
 and Academy Awards. How is JCGL related to CGL? The Japanese
 and Europeans. How the Texas Panhandle contributed to graphics.
 A glimpse at the future. And lots, lots more.


------------------------------

Date: Wed, 3 Jun 1987 21:46:31 EDT
From: (William J. Joel) <JZEM%MARIST.BITNET@wiscvm.wisc.edu>
Subject: Survey: Microcomputers in Graphics Education
Status: RO

Please look at the survey below and determine whether it would be
appropriate for a separate edition of Info-Graphics to cover just
this survey.  I had sent it out recently to 250 institutions world
wide, but only got 38 back.  I could use more responses to make the
survey more substantial.  In any event, I'd like IG readers to be able
to get this survey.  Thanks!
---------------------------------------------------------------------
Hi!
The following survey is intended for computer graphics instructors.
If you are such a person, I would appreciate it if you would print
out the survey, answer it and send it to the address listed below.
Please make sure your name, institution, division/department, and
title are listed somewhere on the returned survey.  Thank you for
your help!
                       ----- CUT HERE -----
1
-
-                                   Survey of
+                                   Survey of
0                               Microcomputers in
+                               Microcomputers in
0                  Undergraduate Computer Graphics Curriculum
+                  Undergraduate Computer Graphics Curriculum
-
           The following survey  has been designed to  determine the rea-
        sons for  and the extent of  the use of microcomputers  in under-
        graduate computer graphics curriculum.  If you are not the prima-
        ry graphics  contact at  your institution,   please forward  this
        survey to that person.
0          Please return this survey to:
0           William J. Joel
            Division of Computer Science & Mathematics
            Marist College
            82 North Road
            Poughkeepsie, NY 12601
            USA
0       Thank you!  Your help in this survey is most appreciated.
1
0       Survey of                                                  page 2
        DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD
-       1.    Indicate the number of each  type of microcomputer for each
              category.   Use  the last three  blanks for any  micros not
              listed.   Any micros that could be counted in more than one
              columns should be so counted.
0             Microcomputer  Avaialble to  Available to
              -------------  all students  graphics stud  To be acquired
              -------------  ------------  -------------  --------------
              IBM PC/XT         _____         _____            _____
              IBM AT            _____         _____            _____
              IBM RT            _____         _____            _____
              Apple IIe/+/GS    _____         _____            _____
              Apple Mac/Lisa    _____         _____            _____
              Amiga             _____         _____            _____
              Tandy             _____         _____            _____
              Commodore         _____         _____            _____
              ____________      _____         _____            _____
              ____________      _____         _____            _____
              ____________      _____         _____            _____
0       2.    Check the three (3) microcomputer attributes most appropri-
              ate for each  column,  as they relate to use  in a computer
              graphics course.   DO NOT check more or less than three for
              each column.
0             Attribute   Most        Least       Reason for   Reason for
              ---------   beneficial  beneficial  prior        future
              ---------   ----------  ----------  acquisition  acquistion
              ---------   ----------  ----------  -----------  ----------
              resolution    _____       _____        _____        _____
              no. of
              colors        _____       _____        _____        _____
              no. of
              bit planes    _____       _____        _____        _____
              amount of
              memory (RAM)
                            _____       _____        _____        _____
              floppy disks
                            _____       _____        _____        _____
              hard disks    _____       _____        _____        _____
              peripheral
              connections   _____       _____        _____        _____
              portability   _____       _____        _____        _____
              size          _____       _____        _____        _____
              cost          _____       _____        _____        _____
              software      _____       _____        _____        _____
              operating
              system        _____       _____        _____        _____
              languages     _____       _____        _____        _____
              CPU           _____       _____        _____        _____
1
0       Survey of                                                  page 3
        DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD
-       3.    Check the three (3) computer graphics topics most appropri-
              ate for each  column,  as they relate  to computer graphics
              curriculum.  DO NOT check more or less than three.
0             Topic          Least       Most
              -----          emphasized  emphasized
              -----          ----------  ----------
              2-D basics        _____       _____
              3-D basics        _____       _____
              hidden
              line/surface
              removal           _____       _____
              shading           _____       _____
              ray tracing       _____       _____
              solid
              modelling         _____       _____
              animation         _____       _____
              fractals          _____       _____
              business
              graphics          _____       _____
              ____________      _____       _____
              ____________      _____       _____
              ____________      _____       _____
0       4.    Do you  feel that microcomputers  are useful in  a computer
              graphics education?
0             (Circle one)     Yes     No     Undecided

------------------------------

Date: Thu, 11 Jun 87 14:47:58 EDT
From: ucbcad!ames!seismo!mimsy!aplcen!aplvax!LOCAL.arpa!djs@ucbvax.Berkeley.EDU (David J. Scheerer)
Subject: Contour plots [C PROGRAM SOURCE]
Organization: The Johns Hopkins University Applied Physics Laboratory
Status: RO

This is a preliminary C routine to contour plot a regular
matrix generated from a equation.  I use the SUN's
GRAPH & PLOT to plot 'em out.

#define   PI  3.141592654
#include <math.h>
	int iub, jub, nc;
	float d[31][31], x[31], y[31], z[10];

main()
{
	int i, j;
	float ix, jy;
	float r;

	iub = 30;
	jub = 30;
	nc = 10;
	for (i = 0; i <= iub; ++i)
	{
	    ix = 2 * PI * (2*i-iub)/iub;
	    for (j = 0; j <= jub; ++j)
	    {
	        jy = 2 * PI * (2 * j - jub)/jub;
	        r = sqrt(ix * ix  +  jy * jy);
	        d[i][j] = sin(r) + .5/sqrt( (ix+3.05)*(ix+3.05) + jy*jy);
	    }
	    x[i] = i;
	}
	for (j = 0; j <= jub; ++j)
	   y[j] = j;
	for (i = 0; i <= nc-1; ++i)
	   z[i] = (float)(i - 5)/5;
	contour();
} 
contour()
{
	/* INPUT VARIABLES TO CONTOUR */
	extern int iub; 	   /* the number of discrete intervals in the horizontal measuerement grid */
	extern int jub; 	   /* the number of discrete intervals in the vertical meausrement grid */
 	extern float d[][31];      /* two dimensional array containing the z values for each (x,y) pair */
	extern float x[];	   /* one dimensional array containing the actual horizontal coordinates of each sample point */
	extern float y[];	   /* one dimensional array containing the actual vertical coordinates of each sample point */
	extern int nc;		   /* the number of contouring levels */
	extern float z[];	   /* one dimensional array containing the contour levels in increasing order */

	/* VARIABLES LOCAL TO CONTOUR */
	float h[5];        /* relative heights of the four corners of the box above the contour */
	int ish[5];	   /* sign of h( ) 2 => above contour, 1=> on contour, 0 => below contour*/
	float xh[5];	   /* x coordinates of four corners of box */
	float yh[5];	   /* y coordinates of four corners of box */
	static int im[4] = {0, 1, 1, 0};    	/* mapping from vertex numbers to x offsets */
	static int jm[4] = {0, 0, 1, 1};	/* mapping from vertex numbers to y offsets */
	int prmerr;	   /* input parameter error 0 => no error, 1 => error */
	static int castab[3][3][3] = {		/* case switch table */
	    { {0,0,8}, {0,2,5}, {7,6,9} },
	    { {0,3,4}, {1,3,1}, {4,3,0} },
	    { {9,6,7}, {5,2,0}, {8,0,0} }
	};
	float dmin;	           /* lowest vertex */
	float dmax;	           /* highest vertex */
	int case_num;
	int i, j, k, m; 	   /* loop indices */
	int m1, m2, m3;
	float x1, y1, x2, y2;      /* coordinates of points to be connected to draw contour segment */



	/* check the input parameters for validity */

	prmerr = 0;
	if (iub <= 0 || jub <= 0) 
	    prmerr = 1;
	if (nc <= 0)
	    prmerr = 1;
	for (k = 1; k <= nc-1; ++k)
	    if (z[k] <= z[k-1])
	        prmerr = 1;
	if (prmerr) 
	{
	    printf("error in input parameters\n");
	    return;
	}



	/* scan the array, top down, left to right */

	for (j = jub-1; j >= 0; --j)
	{ 
	    for (i = 0; i <= iub - 1; ++i)
	    { /* find the lowest vertex */
		dmin = (d[i][j] < d[i][j+1])? d[i][j]: d[i][j+1];
	        if (d[i+1][j] < dmin) 
	            dmin = d[i+1][j];
	        if (d[i+1][j+1] < dmin)
	            dmin = d [i+1][j+1];

	        /* find the highest vertex */
		dmax = (d[i][j] > d[i][j+i])? d[i][j]: d[i][j+1];
	        if (d[i+1][j] > dmax) 
	            dmax = d[i+1][j];
	        if (d[i+1][j+1] > dmax) 
	            dmax = d[i+1][j+1];
		if (dmax >= z[0]  ||  dmin <= z[nc-1]) 
	        {

	            /* draw each contour within this box */
	            for (k = 0; k <= nc-1; ++k)
	            {
		        if (z[k] >=  dmin || z[k] <= dmax)
		    	{
		            for (m = 4; m >= 0; --m)
	                    {
		 	        if (m > 0) 
	                        {
			            h[m] = d[i + im[m-1]][j + jm[m-1]] - z[k];
	                            xh[m] = x[i + im[m-1]];
	                            yh[m] = y[j + jm[m-1]]; 
			        }
	                        if (m == 0)
	                        { 
			            h[0] = (h[1] + h[2] + h[3] + h[4]) / 4;
	                            xh[0] = (x[i] + x[i+1]) / 2;
	                            yh[0] = (y[j] + y[j+1]) / 2; 
			        }
	                        if (h[m] > 0)
			            ish[m] = 2;
	                        else if (h[m] < 0)
			            ish[m] = 0;
	                        else ish[m] = 1;
	                    }

	                    /* scan each triangle in the box */
	                    for (m = 1; m <= 4; ++m)
	                    {     
		   	        m1 = m;
	                        m2 = 0;
	                        m3 = m + 1;
	                        if (m3 == 5)
			            m3 = 1;
	                        case_num = castab[ish[m1]][ish[m2]][ish[m3]];
	                        if (case_num == 0)
			            continue;
	                        switch (case_num)
			        {
	                        case 1:  /* line between vertices m1 and m2 */
			            x1 = xh[m1];
	                            y1 = yh[m1];
	                            x2 = xh[m2];
	                            y2 = yh[m2];
				    break;
	                        case 2:  /* line between vertices m2 and m3 */
	                            x1 = xh[m2];
	                            y1 = yh[m2];
                                    x2 = xh[m3];
	                            y2 = yh[m3];
			            break;
	                        case 3:  /* line between vertices m3 and m1 */
	                            x1 = xh[m3];
	                            y1 = yh[m3];
	                            x2 = xh[m1];
	                            y2 = yh[m1];
				    break;
	                        case 4:  /* line between vertex m1 and side m2-m3 */
	                            x1 = xh[m1];
	                            y1 = yh[m1];
	                            x2 = (h[m3] * xh[m2] - h[m2] * xh[m3]) / (h[m3] - h[m2]);
	                            y2 = (h[m3] * yh[m2] - h[m2] * yh[m3]) / (h[m3] - h[m2]);
				    break;
	                        case 5:  /* line between vertex m2 and side m3-m1 */
	                            x1 = xh[m2];
	                            y1 = yh[m2];
	                            x2 = (h[m1] * xh[m3] - h[m3] * xh[m1]) / (h[m1] - h[m3]);
	                            y2 = (h[m1] * yh[m3] - h[m3] * yh[m1]) / (h[m1] - h[m3]);
				    break;
	                        case 6:  /* line between vertex m3 and side m1-m2 */
	                            x1 = xh[m3];
	                            y1 = yh[m3];
	                            x2 = (h[m2] * xh[m1] - h[m1] * xh[m2]) / (h[m2] - h[m1]);
	                            y2 = (h[m2] * yh[m1] - h[m1] * yh[m2]) / (h[m2] - h[m1]);
				    break;
	                        case 7:  /* line between sides m1-m2 and m2-m3 */
	                            x1 = (h[m2] * xh[m1] - h[m1] * xh[m2]) / (h[m2] - h[m1]);
	                            y1 = (h[m2] * yh[m1] - h[m1] * yh[m2]) / (h[m2] - h[m1]);
	                            x2 = (h[m3] * xh[m2] - h[m2] * xh[m3]) / (h[m3] - h[m2]);
	                            y2 = (h[m3] * yh[m2] - h[m2] * yh[m3]) / (h[m3] - h[m2]);
				    break;
	                        case 8:  /* line between sides m2-m3 and m3-m1 */
	                            x1 = (h[m3] * xh[m2] - h[m2] * xh[m3]) / (h[m3] - h[m2]);
	                            y1 = (h[m3] * yh[m2] - h[m2] * yh[m3]) / (h[m3] - h[m2]);
	                            x2 = (h[m1] * xh[m3] - h[m3] * xh[m1]) / (h[m1] - h[m3]);
	                            y2 = (h[m1] * yh[m3] - h[m3] * yh[m1]) / (h[m1] - h[m3]);
				    break;
				case 9:  /* line between sides m3-m1 and m1-m2 */
	                            x1 = (h[m1] * xh[m3] - h[m3] * xh[m1]) / (h[m1] - h[m3]);
	                            y1 = (h[m1] * yh[m3] - h[m3] * yh[m1]) / (h[m1] - h[m3]);
	                            x2 = (h[m2] * xh[m1] - h[m1] * xh[m2]) / (h[m2] - h[m1]);
	                            y2 = (h[m2] * yh[m1] - h[m1] * yh[m2]) / (h[m2] - h[m1]);
				    break;
			        }
	                    drawit:
			        printf("%6.2f %6.2f\n", x1, y1);
				printf("%6.2f %6.2f\n", x2, y2);
				printf("\");
	                    } /* bottom of m loop */ 
			} /* bottom of inner if */
	            } /* bottom of k loop */
	        } /* bottom of outer if */
	    } /* bottom of i loop */
	} /* bottom of j loop */
} /* bottom of contour subroutine */



------------------------------

End of INFO-GRAPHICS
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