Single mandelbrot drawing function in C++ using GLUT

mandelbrot.cpp

#include <stdlib.h>
#include "GL/glut.h"
#include <iostream>
#pragma comment(lib, "glut32.lib")
#define WINDOW_TITLE "Project"
using namespace std;

const float ANGLE = 45.f;
const float FOV = 70.f;
const float NCP = 0.001f;
const float FCP = 40.f;
int m_iWidth = 800;		//width of the viewport
int m_iHeight = 600;	//height of the viewport

///
/// Function designed to be use in the glutKeyboardFunc
/// @param key represents the key pressed in the keyboard
/// 
void keyboardDown(unsigned char key, int x, int y) 
{
 
  switch(key) {
  case 'Q':
  case 'q':
  case  27:   // ESC
	  exit(0);
  }
}

void idle(void)
{
	glutPostRedisplay();
}

#define NUM 100
int dwell(double cx, double cy)
{
	double tmp, dx = cx, dy = cy, fsq = cx*cx + cy*cy;
	int count = 0;
	for (count = 0; count <= NUM && fsq <= 4; count++) 
	{
		tmp = dx;
		dx = dx*dx - dy*dy + cx;
		dy = 2.0 * tmp * dy + cy;
		fsq = dx*dx + dy*dy;
	}
	return count;
}

void Color(int iterations) 
{
	if (iterations < 10)
		glColor3ub(64, 128, 128);
	else if (iterations < 30)
		glColor3ub(0, 0, 255);
	else if (iterations < 50)
		glColor3ub(0, 255, 0);
	else if (iterations < 70)
		glColor3ub(255, 0, 0);
	else if (iterations < 90)
		glColor3ub(255, 255,0);
	else 
		glColor3ub(0, 128, 0);
}

double interpolate(double a, double b, double value) 
{
	return a + ((b - a)* value);
}

void draw()
{
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	glClearColor(0.6, 0.6, 0.6, 1);
	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();

	//begin - rendering a simple triangle (testing)
	float xstart = -2.25;
	float xend = 0.75;
	float ystart = -1.5;
	float yend = 1.5;
	for (int y = 0; y < m_iHeight; y++) 
	{
		for (int x = 0; x < m_iWidth; x++) 
		{
			double mapX = x / (double)m_iWidth;
			double mapY = y / (double)m_iHeight;
			glBegin(GL_POINTS);
			Color(dwell(interpolate(xstart, xend, mapX), interpolate(ystart, yend, mapY)));
				glVertex2i(x, y);
			glEnd();
		}
	}
  //begin - rendering a simple triangle
	glutSwapBuffers();
}

void reshape(int width, int height) 
{
  glViewport (0, 0, (GLsizei) width, (GLsizei) height);
 
  glMatrixMode (GL_PROJECTION);
  glLoadIdentity();	
  m_iWidth = width;
  m_iHeight = height;
  gluOrtho2D(0, width, 0, height);

  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
}

bool initialize()
{
	glEnable(GL_DEPTH_TEST);
	return true;
}

int main(int argc, char** argv)
{
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH);
	glutInitWindowSize(m_iWidth, m_iHeight);
	glutCreateWindow(WINDOW_TITLE);	
	glutCreateMenu(NULL);
	if(!initialize()) return 1;
	glutDisplayFunc(draw);
	glutIdleFunc(idle);
	glutReshapeFunc(reshape);
	glutKeyboardFunc(keyboardDown);
	//GUI construction
	glutMainLoop();
	return 0;
}