From: "Mark Fleig" <markfleig AT worldnet DOT att DOT net>
Newsgroups: comp.os.msdos.djgpp,rec.games.programmer
Subject: Allegro plasma routine
Date: 6 Oct 1996 04:52:23 GMT
Organization: AT&T WorldNet Services
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To: djgpp AT delorie DOT com
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Here it is. Hope it works. (did for me anyway.)

-fleig

-- 
=============================================================
mark fleig                                        
markfleig AT worldnet DOT att DOT net
mfleig AT juno DOT com

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/* 
 *    plasma2.c: Allegro routine for fractal plasma clouds. (Oct.96) 
 * 
 *    This is a port to Allegro of the Fractint plasma routine posted by 
 *    Cory Bloyd. It uses the old divide and adjust routines, and accepts
 *    keyboard commands to change graininess and random seed instead
 *    of command line parameters. Enjoy.   -mark fleig
 *
 *    How to make the routine better:
 *    1) Scrap putpixel() and getpixel() and use direct memory access.
 *    2) Use the newer plasma routines. They're probably more efficient.
 *    3) Knock the resolution up to 800x600. Looks great.
 */

/* Here is the original header block from Cory:
 * plasma
 *   Random, cloud-like formations.  Requires 4 or more colors.
 *   A recursive algorithm repeatedly subdivides the screen and
 *   colors pixels according to an average of surrounding pixels
 *   and a random color, less random as the grid size decreases.
 *   Three parameters: 'graininess' (.5 to 50, default = 2), old/new
 *   algorithm, seed value used.
 */

#include <stdlib.h>
#include <stdio.h>
#include "allegro.h"


static int iparmx;				/* iparmx = parm.x * 16 */
static int shiftvalue;				/* shift based on #colors */
static int pcolors;

/*-------------------------------------------
 * Random adjustment of the current pixel box.
 *-------------------------------------------*/
static int adjust(int xa,int ya,int x,int y,int xb,int yb)
{
   long pseudorandom;

   pseudorandom = ((long)iparmx)*((random() % 32766)-16383);
   pseudorandom = pseudorandom*(abs(xa-xb)+abs(ya-yb));
   pseudorandom = pseudorandom >> shiftvalue;
   pseudorandom = ((getpixel(screen,xa,ya)+getpixel(screen,xb,yb)+1)>>1)+
pseudorandom;

   if (pseudorandom <	1) pseudorandom =   1;
   if (pseudorandom >= pcolors) pseudorandom = pcolors-1;
   putpixel(screen, x, y, (int)pseudorandom);

   return((int)pseudorandom);
}

/*-------------------------------------------
 * Semi-recursive division of the current box.
 * Keep subdividing until the size of the box 
 * is one pixel wide. Then drop out to the next
 * iteration.
 *-------------------------------------------*/
static void subDivide(int x1,int y1,int x2,int y2)
{
   int x,y;
   int v,i;

   if(x2-x1<2 && y2-y1<2)
      return;
   if(keypressed()) 
	return;
   x = (x1+x2)>>1;
   y = (y1+y2)>>1;
   if((v=getpixel(screen,x,y1)) == 0)
       v=adjust(x1,y1,x ,y1,x2,y1);
   i=v;
   if((v=getpixel(screen,x2,y)) == 0)
       v=adjust(x2,y1,x2,y ,x2,y2);
   i+=v;
   if((v=getpixel(screen,x,y2)) == 0)
       v=adjust(x1,y2,x ,y2,x2,y2);
   i+=v;
   if((v=getpixel(screen,x1,y)) == 0)
       v=adjust(x1,y1,x1,y ,x1,y2);
   i+=v;

   if(getpixel(screen,x,y) == 0)
      putpixel(screen,x,y,(i+2)>>2);

   subDivide(x1,y1,x ,y);
   subDivide(x ,y1,x2,y);
   subDivide(x ,y ,x2,y2);
   subDivide(x1,y ,x ,y2);
}


/*-------------------------------------------
 * Main routine: Fill the pallete and place 
 * random color dots in each corner of the screen.
 * This is the first box to begin subdivision. The
 * subDivide() routine will begin with these four
 * color points and average the center pixel, splitting
 * the big box into four smaller boxes for further
 * division. As the boxes get smaller, the amount of
 * randomness is reduced to smooth color transitions.
 *-------------------------------------------*/
void main()
{
   PALLETE dacbox;
   RGB Red    = {
      63, 0, 0	 };
   RGB Green  = {
      0,63, 0	};
   RGB Blue   = {
      0, 0,63	};

   int c,i;
   int x, y;
   int rseed;

   iparmx = 16;
   shiftvalue = 18;
   rseed = 2;

   allegro_init();
   install_keyboard(); 
   set_gfx_mode(GFX_VGA, 320, 200, 0, 0);

   dacbox[0].r  = 0 ;
   dacbox[0].g= 0 ;
   dacbox[0].b = 0 ;

   for(i=1;i<=85;i++)
   {
      dacbox[i].r = (i*Green.r + (86-i)*Blue.r)/85;
      dacbox[i].g = (i*Green.g + (86-i)*Blue.g)/85;
      dacbox[i].b = (i*Green.b + (86-i)*Blue.b)/85;

      dacbox[i+85].r = (i*Red.r + (86-i)*Green.r)/85;
      dacbox[i+85].g = (i*Red.g + (86-i)*Green.g)/85;
      dacbox[i+85].b = (i*Red.b + (86-i)*Green.b)/85;

      dacbox[i+170].r = (i*Blue.r + (86-i)*Red.r)/85;
      dacbox[i+170].g = (i*Blue.g + (86-i)*Red.g)/85;
      dacbox[i+170].b = (i*Blue.b + (86-i)*Red.b)/85;
   }

   set_pallete(dacbox);

/*---------------------------------------------------------------------*/
   clear_keybuf();
   clear(screen);

   while (!key[KEY_ESC]) {
   if (key[KEY_LEFT]) {rseed--; clear(screen);}
   if (key[KEY_RIGHT]) {rseed++; clear(screen);}
   if (key[KEY_UP]) {iparmx += 1; clear(screen);}
   if (key[KEY_DOWN]) {iparmx -= 1; clear(screen); }
   if (!key[KEY_ESC]) clear_keybuf();

   if (iparmx < 0) iparmx = 0;
   srand(rseed);
   pcolors = 255;
   putpixel(screen,0,0,1+(((rand()/pcolors)
	                  *(pcolors-1))>>(shiftvalue-11)));
   putpixel(screen,SCREEN_W-1,0,1+(((rand()/pcolors)
			  *(pcolors-1))>>(shiftvalue-11)));
   putpixel(screen,SCREEN_W-1,SCREEN_H-1,1+(((rand()/pcolors)
		          *(pcolors-1))>>(shiftvalue-11)));
   putpixel(screen,0,SCREEN_H-1,1+(((rand()/pcolors)
			  *(pcolors-1))>>(shiftvalue-11)));
   subDivide(0,0,SCREEN_W-1,SCREEN_H-1);

   }
/*------------------------------------------------------------------*/
   clear_keybuf();
   exit(0);
}
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