//rotating cube program


//www.timestocome.com
//to link under OSX gcc -framework OpenGL -framework GLUT -o cube cube.c


#include <stdio.h>
#include <GLUT/glut.h>

static GLfloat theta[]= {0.0, 0.0, 0.0};
static GLint axis = 2;



GLfloat vertices[][3] = {		//the 8 vertices of a cube
	{-1.0, -1.0, -1.0},
	{ 1.0, -1.0, -1.0},
	{ 1.0,  1.0, -1.0},
	{-1.0,  1.0, -1.0},
	{-1.0, -1.0,  1.0},
	{ 1.0, -1.0,  1.0},
	{ 1.0,  1.0,  1.0},
	{-1.0,  1.0,  1.0}

};





GLfloat colors[][3] = {			//one color per vertice
	{0.0, 0.0, 0.0},
	{1.0, 0.0, 0.0},
	{0.0, 1.0, 0.0},
	{0.0, 0.0, 1.0},
	{1.0, 1.0, 0.0},
	{1.0, 0.0, 1.0},
	{0.0, 1.0, 1.0},
	{1.0, 1.0, 1.0}

};





void polygon (int a, int b, int c, int d){



	//draw a side of the cube and assign colors
	glBegin(GL_POLYGON);

		glColor3fv(colors[a]);
		glVertex3fv(vertices[a]);

		glColor3fv(colors[b]);
		glVertex3fv(vertices[b]);

		glColor3fv(colors[c]);
		glVertex3fv(vertices[c]);

		glColor3fv(colors[d]);
		glVertex3fv(vertices[d]);

	glEnd();

}



void colorcube(void){


	//map vertices to faces
	//order is very important!!

	polygon(0, 3, 2, 1);
	polygon(2, 3, 7, 6);
	polygon(0, 4, 7, 3);
	polygon(1, 2, 6, 5);
	polygon(4, 5, 6, 7);
	polygon(0, 1, 5, 4);
}





void display(void){

	//display callback, 
	//clear frame buffer and z buffer
	//rotate cube 
	//and draw

	//clear viewport buffer (color and depth buffers)
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	glLoadIdentity();			//replace current matrix w/ identity..
						// else see shadow/flicker of last image



	//multiply current matrix by rotation matrix, theta, x, y, z
	glRotatef(theta[0], 1.0, 0.0, 0.0);
	glRotatef(theta[1], 0.0, 1.0, 0.0);
	glRotatef(theta[2], 0.0, 0.0, 1.0);

	colorcube();

	glFlush();					//probably a good idea but no effect on this program

	glutSwapBuffers();			//put image to be drawn in buffer for display

}



void spinCube(void){

	//idle callback
	//spin cube 2 degrees

	theta[axis] += 0.05;        //degrees each frame smaller means slower turning cube
	if(theta[axis] > 360.0){
		theta [axis] -= 360.0;
	}

	display();

}

	

void mouse(int btn, int state, int x, int y){

	//selects an axis to rotate about
	if(btn == GLUT_LEFT_BUTTON && state == GLUT_DOWN){axis = 0;}
	if(btn == GLUT_RIGHT_BUTTON && state == GLUT_DOWN){axis = 1;}
	if(btn == GLUT_MIDDLE_BUTTON && state == GLUT_DOWN){axis = 3;}



}



void myReshape(int w, int h){

//	glViewport( 0, 0, w, h);	//sets viewport... not needed here

	glMatrixMode(GL_PROJECTION);//which matrix stack to perform following ops on
	glLoadIdentity();			//reduces flicker but no effect in this program

	if( w <= h){
		glOrtho( -2.0, 2.0, -2.0*((GLfloat)h/(GLfloat)w), 
			2.0*((GLfloat)h/(GLfloat)w), -10.0, 10.0);

	}else{
		glOrtho( -2.0*((GLfloat)w/(GLfloat)h), 2.0*((GLfloat)w/(GLfloat)h), -2.0,
			2.0, -10.0, 10.0);
	}

	glMatrixMode(GL_MODELVIEW);	//switch to operating on modelview matrix

}



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

		glutInit(&argc, argv);

		glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
		glutInitWindowSize( 500, 500);
		glutCreateWindow("rotating cube");
		glutReshapeFunc(myReshape);
		glutDisplayFunc(display);
		glutIdleFunc(spinCube);
		glutMouseFunc(mouse);
		glEnable(GL_DEPTH_TEST);			//enable hidden surface removal

		glutMainLoop();


		return 0;

}