/* flat and non-flat assemblies of triangles */

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

GLfloat vertices[][3] = { { -1.5, -0.5, 0 }, { -0.5, -0.5, 0 }, { -0.5, 0.5,
		0 }, { -1.5, 0.5, 0 }, { -1, 0, 1.0 },
		{  1.5, -0.5, 0 }, { 0.5, -0.5, 0 },
		{ 0.5, 0.5, 0 }, { 1.5, 0.5, 0 }, {1, 0, 0}};

GLfloat colors[][3] = { { 0.0, 0.0, 0.0 }, { 1.0, 0.0, 0.0 }, { 1.0, 1.0, 0.0 },
		{ 0.0, 1.0, 0.0 }, { 0.0, 0.0, 1.0 }, { 1.0, 0.0, 1.0 },
		{ 1.0, 1.0, 1.0 }, { 0.0, 1.0, 1.0 } };

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

	glBegin(GL_POLYGON);
	glColor3fv(colors[col]);
	glVertex3fv(vertices[a]);
	glVertex3fv(vertices[b]);
	glVertex3fv(vertices[c]);
	glEnd();
}

void colorcube() {
	glEnableClientState(GL_VERTEX_ARRAY);
	polygon(1, 0, 1, 4);
	polygon(2, 1, 2, 4);
	polygon(3, 2, 3, 4);
	polygon(4, 3, 0, 4);

	polygon(1, 5, 6, 9);
	polygon(2, 6, 7, 9);
	polygon(3, 7, 8, 9);
	polygon(4, 8, 5, 9);

}

static GLfloat theta[] = { 0.0, 0.0, 0.0 };
static GLint axis = 2;
static GLdouble viewer[] = { 0.0, 0.0, 5.0 }; /* initial viewer location */

void display() {

	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

	/* update viewer position in model-view matrix */

	glLoadIdentity();
	gluLookAt(viewer[0], viewer[1], viewer[2], 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);

	/* rotate cube */

	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();
	glutSwapBuffers();
}

void mouse(int btn, int state, int x, int y) {
	if (btn == GLUT_LEFT_BUTTON && state == GLUT_DOWN)
		axis = 0;
	if (btn == GLUT_MIDDLE_BUTTON && state == GLUT_DOWN)
		axis = 1;
	if (btn == GLUT_RIGHT_BUTTON && state == GLUT_DOWN)
		axis = 2;
	theta[axis] += 2.0;
	if (theta[axis] > 360.0)
		theta[axis] -= 360.0;
	display();
}

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

	/* use x, X, y, Y, z, and Z keys to move viewer */

	if (key == 'x')
		viewer[0] -= 1.0;
	if (key == 'X')
		viewer[0] += 1.0;
	if (key == 'y')
		viewer[1] -= 1.0;
	if (key == 'Y')
		viewer[1] += 1.0;
	if (key == 'z')
		viewer[2] -= 1.0;
	if (key == 'Z')
		viewer[2] += 1.0;
	display();
}

void myReshape(int w, int h) {
	glViewport(0, 0, w, h);

	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	// use a perspective view
/*
	if (w <= h)
		glFrustum(-2.0, 2.0, -2.0 * (GLfloat) h / (GLfloat) w,
				2.0 * (GLfloat) h / (GLfloat) w, 2.0, 20.0);
	else
		glFrustum(-2.0, 2.0, -2.0 * (GLfloat) w / (GLfloat) h,
				2.0 * (GLfloat) w / (GLfloat) h, 2.0, 20.0);
*/
	/* or we can use gluPerspective */
	/* gluPerspective(45.0, w/h, 1.0, 10.0); */

	// or use an orthographic view
	glOrtho(-2.0, 2.0, -2.0, 2.0, 2.0, 20.0);

	glMatrixMode(GL_MODELVIEW);
}

int main(int argc, char **argv) {
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
	glutInitWindowSize(500, 500);
	glutCreateWindow("colorcube");
	glutReshapeFunc(myReshape);
	glutDisplayFunc(display);
	glutMouseFunc(mouse);
	glutKeyboardFunc(keys);
	glEnable(GL_DEPTH_TEST);
	//glEnable(GL_CULL_FACE);
	glutMainLoop();
	return 0;
}