// Fog is used in most games, to help simulate both the size 
// and reality of an area. for the fog to work well do this:

// Enable the depth testing, enable the fog, choose the fog
// mode, choose the fog color, chose the fog density and how
// well it looks. 

// You can also set the starting and ending distances
// for the fog, but this is enough for now.

// You will be able to see how it is done from the code below.

#include <GL/gl.h>
#include <GL/glut.h>

GLfloat angle = 0.0;

GLfloat density = 0.3; //set the density to 0.3 which is acctually quite thick
GLfloat fogColor[4] = {0.5, 0.5, 0.5, 1.0}; //set the for color to grey

void cube (void) {
	glRotatef(angle, 1.0, 0.0, 0.0);
	glRotatef(angle, 0.0, 1.0, 0.0);
	glRotatef(angle, 0.0, 0.0, 1.0);
	glColor3f(1.0, 0.0, 0.0);
	glutSolidCube(2);
}

void init (void) {
	glEnable (GL_DEPTH_TEST); //enable the depth testing
	glEnable (GL_FOG); //enable the fog
    glFogi (GL_FOG_MODE, GL_EXP2); //set the fog mode to GL_EXP2
    glFogfv (GL_FOG_COLOR, fogColor); //set the fog color to our color chosen above
    glFogf (GL_FOG_DENSITY, density); //set the density to the value above
    glHint (GL_FOG_HINT, GL_NICEST); // set the fog to look the nicest, may slow down on older cards
}

void display (void) {
	glClearColor (0.0,0.0,0.0,1.0);
    glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glLoadIdentity();  
	gluLookAt (0.0, 0.0, 5.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
	cube();
	glutSwapBuffers();
	angle ++;
}

void reshape (int w, int h) {
	glViewport (0, 0, (GLsizei)w, (GLsizei)h);
	glMatrixMode (GL_PROJECTION);
	glLoadIdentity ();
	gluPerspective (60, (GLfloat)w / (GLfloat)h, 1.0, 100.0);
	glMatrixMode (GL_MODELVIEW);
}

int main (int argc, char **argv) {
    glutInit (&argc, argv);
	glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH);
	glutInitWindowSize (500, 500);
	glutInitWindowPosition (100, 100);
    glutCreateWindow ("A basic OpenGL Window");
	init ();
    glutDisplayFunc (display);
	glutIdleFunc (display);
	glutReshapeFunc (reshape);
    glutMainLoop ();
    return 0;
}