/* 

 *

 *    This application has was created by Timothy A. Graupmann. For

 *    any questions or comments send email to tgraupmann@yahoo.com.

 *

 *    This application displays the Julia Fractal while allowing the

 *    user to navigate and manipulate the fractal. The arrow keys

 *    scroll accordingly while "*" and "/" increase and decrease

 *    fractal iterations. "+" and "-" zoom in and out.

 *

 */





#include <math.h>

#include <GL/glut.h>



typedef struct { float x, y; } Complex;

static int max_level=10;

static double hscal=0.0045;

static double wscal=0.0045;

static double htran=0.0;

static double wtran=0.0;



void gfxInit(void);

void reshape(int w, int h);

void keyboard(unsigned char key,int x, int y);

double magnitude(Complex c);

void julia (int w, int h, float max_level);

void display(void);

Complex complexSquare (Complex c);





void gfxInit(void){

	glClearColor(0.0, 0.0, 0.0, 0.0);

	glShadeModel(GL_FLAT);

	glClear(GL_COLOR_BUFFER_BIT);

}

void reshape(int w, int h){


	glViewport(0, 0, (GLsizei)w, (GLsizei)h);

	glMatrixMode(GL_PROJECTION);

	glLoadIdentity();

	gluOrtho2D(0.0, (GLdouble)w, 0.0, (GLdouble)h);

}

void keyboard(unsigned char key,int x, int y) {

	switch(key) {

		case 'q':case 'Q':

			exit(0);

			break;

		case '*':

			max_level++;

			display();

			break;

		case '/':

			max_level--;

			if(max_level<=2)

				max_level=3;

			display();

			break;

		case '8':

			htran+=50.0*hscal;

			display();

			break;

		case '6':

			wtran+=50.0*wscal;

			display();

			break;

		case '4':

			wtran-=50.0*wscal;

			display();

			break;

		case '2':

			htran-=50.0*hscal;

			display();

			break;

		case '+':

			hscal*=0.50;

			wscal*=0.50;

			display();

			break;

		case '-':

			hscal/=0.50;

			wscal/=0.50;

			display();

			break;

		case '5':

			max_level=20;

			hscal=0.0016;

			wscal=0.0016;

			htran=0.0;

			wtran=0.0;

			display();

	}	

}

double magnitude(Complex c){

	return sqrt(c.x*c.x+c.y*c.y);

}

void julia (int w, int h) {

	Complex c,z;

	double color;

	int level=0;	

	c.x=.5;

	c.y=.5;

	int x,y=0;

	glBegin(GL_POINTS);

	double aa=-hscal*h+htran;

	double ab=hscal*h+htran;

	double ac=hscal*2.0;

	double ba=-wscal*w+wtran;

	double bb=wscal*w+wtran;

	double bc=wscal*2.0;	

	for(double j=aa;j<ab;j+=ac,x=0,y++) {		

		for(double i=ba;i<=bb;i+=bc,x++,z.x=i,z.y=j,level=0) {

			while ((z.x * z.x + z.y * z.y <= 4.0) && (level< max_level)) {

				z = complexSquare (z);

				z.x += c.x;

				z.y += c.y;

				level++;

			}

			while((magnitude(z)<magnitude(c))&&(level<max_level-1)) {

				z.x+=magnitude(z)-magnitude(c);

				z.y+=magnitude(z)-magnitude(c);

				level++;

			}			

			color=double(level)/double(max_level);			

			if(color<0.3)

				glColor3d(color/0.3,0,0);

			else

				if(color<0.6)

					glColor3d(0,(color-0.3)/0.3,0);

				else

					if(color<0.9)

						glColor3d(0,0,(color-0.6)/0.3);

					else

						glColor3d(0,0,0);

			glVertex2i(x,y);

		}

	}

	glEnd();

}	

void display(void){	

	int w = glutGet(GLUT_WINDOW_WIDTH);

	int h = glutGet(GLUT_WINDOW_HEIGHT);

	julia(w,h);

	glFlush();

	glutSwapBuffers();

}

int main(int argc, char** argv){

	glutInit(&argc, argv);

	glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGB);

	glutInitWindowSize(640,480);

	glutInitWindowPosition(1, 1);

	glutCreateWindow("Julia Fractal");

	gfxInit();

	glutDisplayFunc(display);

	glutReshapeFunc(reshape);

	glutKeyboardFunc(keyboard);	

  	glutMainLoop();

	return 0;

}



Complex complexSquare (Complex c){

	Complex cSq;

	cSq.x = c.x * c.x - c.y * c.y;

	cSq.y = 2 * c.x * c.y;

	return (cSq);

}