//+-------------------------------------------------------------------------+
//+ Program TCHEBY.CPP - November 13, 1994                                  +
//+                                                                         +
//+ By Fausto Arinos de Almeida Barbuto, Rio de Janeiro, RJ, BRAZIL         +
//+ E-mails: BJ06@C53000.PETROBRAS.ANRJ.BR  and  barbuto@ax.ibase.org.br    +
//+                                                                         +
//+ Repeated iterations over the Tschebysheff function over the real domain.+
//+ Based on Pseudocode 15.1 (see REFERENCE below)                          +
//+ Press ESC at any time to fade the screen out and quit.                  +
//+                                                                         +
//+ REFERENCE: Pickover, Clifford A. "Computers, Pattern, Chaos and Beauty" +
//+            1990, St.-Martin's Press, pp. 293.                           +
//+                                                                         +
//+ Uses SVGA256.BGI by Jordan Powell Hargrave and fade-out routine by      +
//+ Michael E. Sargent and Quintessential Sophistry.                        +
//+                                                                         +
//+ Version for spanky.triumf.ca (142.90.112.1), Vancouver, B.C. Canada.    +
//+*************************************************************************+

#include <graphics.h>
#include <stdio.h>
#include <dos.h>
#include <conio.h>
#include <math.h>
#include "svga256.h"

int Video; /* Global variable */

double Chebyshev(int, double);
void fade(void);

int huge DetectSVGA256()
{
  printf("\n Which video mode would you like to use? \n\n");
  printf(" 0 - 320x200x256\n");
  printf(" 1 - 640x400x256\n");
  printf(" 2 - 640x480x256 (suggested when available)\n");
  printf(" 3 - 800x600x256\n");
  printf(" 4 - 1024x768x256\n\n> ");
  scanf("%d",&Video);
  if ((Video>4) || (Video<0)) Video = 2;
  return Video;
}

void main()
{
      double xmin=-1.0, xmax=1.0, ymin=-1.0, ymax=1.0;
      double xold, yold, r, deltap, deltaq, p, q, x, y, T1, T2, h;
      unsigned int maxiter;
      register int k, np, nq;
      int npix, npiy, order, initcolour, graphdriver=DETECT, graphmode;
//
      clrscr();
      printf("\n Program CHEBY.C - By Fausto A. A. Barbuto, November 1994");
      printf("\n\n WARNING: Some combinations of high 'order', 'h' and");
      printf(" 'maxiter' may cause\n          overflow before the end");
      printf(" of the execution.");
      printf("\n\n Select the order of the polynomial (3 <= order <= 20):");
      printf("\n\n> ");
      scanf("%d",&order);
      if ((order < 3) || (order > 20)) order = 10;
      printf("\n Select a step 'h', 0.0 < h < 1.0 (suggested: 0.1):\n\n> ");
      scanf("%lf",&h);
      printf("\n\n Select the maximum number of iterations");
      printf("\n (Suggestion: start with 20, then increase):\n\n> ");
      scanf("%u",&maxiter);
      clrscr();
      printf("\n Choose a colour scheme:\n\n    'Tropical'    : Enter 30\n");
      printf("    Shades of gray: Enter 16\n    Your own      : ");
      printf("Enter ???\n\n> ");
      scanf("%d",&initcolour);

      installuserdriver("Svga256",DetectSVGA256);
      initgraph(&graphdriver,&graphmode,"C:\\BORLANDC\\BGI");

      cleardevice();

      if (Video == 0) {npix=320;  npiy=200;}
      if (Video == 1) {npix=640;  npiy=400;}
      if (Video == 2) {npix=640;  npiy=480;}
      if (Video == 3) {npix=800;  npiy=600;}
      if (Video == 4) {npix=1024; npiy=768;}

      deltap = (xmax-xmin)/(double)(npix-1);
      deltaq = (ymax-ymin)/(double)(npiy-1);

      for (np=0; np<=npix-1; np++) {
	p = xmin + (double)np*deltap;
	for (nq=0; nq<=npiy-1; nq++) {
	  q = ymin + (double)nq*deltaq;
	  x = p; y = q;
	  k = 0;
	  do {
	    xold = x; yold = y;
	    T1 = Chebyshev(order,yold);
	    x = x - h*sin(T1);
	    T2 = Chebyshev(order,xold);
	    y = y + h*sin(T2);
	    r = sqrt(T1*T1 + T2*T2);
	    k++;

	    if (r >= maxiter) {
	      putpixel(np,nq,(initcolour+k));
	    }

	    if (k == maxiter) {
	      putpixel(np,nq,1);
	    }

	  } while (r<=maxiter && k<=maxiter);
	}
	if (kbhit()) break;
      }
      getch();
      fade();
      closegraph();
}

double Chebyshev(int nn, double xx)
{
   double z3, Tc[20], T;
   register int ii;

     z3 = xx*xx*xx;
     Tc[2] = 2.0*xx*xx - 1.0;
     Tc[3] = 4.0*z3 - 3.0*xx;
     for (ii=3;ii<=nn;ii++) {
       Tc[ii+1] = 2.0*xx*Tc[ii] - Tc[ii-1];
       T = Tc[ii+1];
     }
     return T;
}
//+======================================================================+
// Fade-out routine by Michael E. Sargent & The Quintessential Sophistry +
//=======================================================================+
#pragma warn -eff
void fade(void)
{
   int a, b, p1, p2, p3;

   for (a=0; a<64; a++)
   {
      for (b=0; b<256; b++)
      {
	 outp(0x3C7, b);
	 p1 = inp(0x3C9);
	 p2 = inp(0x3C9);
	 p3 = inp(0x3C9);
	 outp (0x3C8, b);
	 if (p1 > 0) outp(0x3C9, p1 - 1);
	    else outp(0x3C9, 0);
	 if (p2 > 0) outp(0x3C9, p2 - 1);
	    else outp(0x3C9, 0);
	 if (p3 > 0) outp(0x3C9, p3 - 1);
	    else outp(0x3C9, 0);
      }
   delay(75);
   }
}
#pragma warn +eff