// Now material lighting lets you color certain objects.
// Using the color command, we are still setting the color
// of the object, but it does not show when we turn on the
// lights, why? This is because the color of the object
// does not matter. What matters is the color of the Material (skin)
// of the object.

// So respectively we change the:
// glColor3f(...);
// to:
// glMaterialfv (GL_FRONT, GL_DIFFUSE, redDiffuseMaterial); 

// Now this new command sets the Material Values, to make it
// red we choose the color of the DIFFUSE light, or direct lighting
// if I am not mistaken. We are also setting the FRONT of the object
// to do this only. As there is no point if there is a light behind it.
// We would just see black anyway if that was the case.

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

GLfloat angle = 0.0;

GLfloat redDiffuseMaterial[] = {1.0, 0.0, 0.0}; //set the material to red

void cube (void) {
	glMaterialfv (GL_FRONT, GL_DIFFUSE, redDiffuseMaterial); //replaces glColor3f(...);
	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); has now been replaced
	glutSolidCube(2);
}

void init (void) {
	glEnable (GL_DEPTH_TEST);
	glEnable (GL_LIGHTING);
	glEnable (GL_LIGHT0);
}

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_DEPTH);
	glutInitWindowSize (500, 500);
	glutInitWindowPosition (100, 100);
    glutCreateWindow ("A basic OpenGL Window");
	init ();
    glutDisplayFunc (display);
	glutIdleFunc (display);
	glutReshapeFunc (reshape);
    glutMainLoop ();
    return 0;
}