/* mandlebrot.c   */

/* E. Angel, Interactive Computer Graphics */
/* A Top-Down Approach with OpenGL, Third Edition */
/* Addison-Wesley Longman, 2003 */

/* Draws the mandlebrot set with hardcoded values */
#include <stdio.h>
#include <stdlib.h>#include <GL/glut.h>/* Defaut data via command line *//* Can enter other values via command line arguments */#define CENTERX -0.5#define CENTERY 0.5#define HEIGHT 0.5#define WIDTH 0.5#define MAX_ITER 100/* N x M array to be generated */#define N 500#define M 500float height = HEIGHT; /* size of window in complex plane */float width = WIDTH;float cx = CENTERX; /* center of window in complex plane */float cy = CENTERY; int max = MAX_ITER; /* number of interations per point */int n=N;int m=M;/* Use unsigned bytes for image */GLubyte image[N][M];/* Complex data type and complex add, mult, and magnitude functions *//* Probably not worth overhead */typedef float complex[2];void add(complex a, complex b, complex p){    p[0]=a[0]+b[0];    p[1]=a[1]+b[1];}void mult(complex a, complex b, complex p){    p[0]=a[0]*b[0]-a[1]*b[1];    p[1]=a[0]*b[1]+a[1]*b[0];}float mag2(complex a){    return(a[0]*a[0]+a[1]*a[1]);}void form(float a, float b, complex p){    p[0]=a;    p[1]=b;}void display(){    glClear(GL_COLOR_BUFFER_BIT);    glDrawPixels(n,m,GL_COLOR_INDEX, GL_UNSIGNED_BYTE, image);}void myReshape(int w, int h){    glViewport(0, 0, w, h);    glMatrixMode(GL_PROJECTION);    glLoadIdentity();    if (w <= h)    gluOrtho2D(0.0, 0.0, (GLfloat) n, (GLfloat) m* (GLfloat) h / (GLfloat) w);    else    gluOrtho2D(0.0, 0.0, (GLfloat) n * (GLfloat) w / (GLfloat) h,(GLfloat) m);    glMatrixMode(GL_MODELVIEW);    display();}void myinit(){    float redmap[256], greenmap[256],bluemap[256];    int i;    glClearColor (1.0, 1.0, 1.0, 1.0);    gluOrtho2D(0.0, 0.0, (GLfloat) n, (GLfloat) m);/* Define pseudocolor maps, ramps for red and blue,   random for green */    for(i=0;i<256;i++)     {         redmap[i]=i/255.;         greenmap[i]=rand()%255;         bluemap[i]=1.0-i/255.;    }    glPixelMapfv(GL_PIXEL_MAP_I_TO_R, 256, redmap);    glPixelMapfv(GL_PIXEL_MAP_I_TO_G, 256, greenmap);    glPixelMapfv(GL_PIXEL_MAP_I_TO_B, 256, bluemap); }main(int argc, char *argv[]){    int i, j, k;    float x, y, v;    complex c0, c, d;    for (i=0; i<n; i++) for(j=0; j<m; j++)     {/* starting point */    x= i *(width/(n-1)) + cx -width/2;    y= j *(height/(m-1)) + cy -height/2;    form(0,0,c);    form(x,y,c0);/* complex iteration */    for(k=0; k<max; k++)        {        mult(c,c,d);        add(d,c0,c);        v=mag2(c);        if(v>4.0) break; /* assume not in set if mag > 4 */        }/* assign gray level to point based on its magnitude */        if(v>1.0) v=1.0; /* clamp if > 1 */        image[i][j]=255*v;    }    glutInit(&argc, argv);    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB );    glutInitWindowSize(N, M);    glutCreateWindow("mandlebrot");    myinit();    glutReshapeFunc(myReshape);    glutDisplayFunc(display);    glutMainLoop();}