#include <GL/glut.h>

#include <math.h>

float angle = 0.0f;


void changeSize(int w, int h)
{
	if (h == 0) h = 1;
	float ratio =  w * 1.0 / h;
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	glViewport(0, 0, w, h);
	gluPerspective(45.0f, ratio, 0.1f, 100.0f);

	glMatrixMode(GL_MODELVIEW);
}

void myRotatef(GLfloat a, GLfloat x, GLfloat y, GLfloat z)
{
	a = a * 3.14 / 18.0; // convert to radians
	GLfloat s = sin(a);
	GLfloat c = cos(a);
	GLfloat t = 1.0 - c;

	GLfloat tx = t * x;
	GLfloat ty = t * y;
	GLfloat tz = t * z;

	GLfloat sz = s * z;
	GLfloat sy = s * y;
	GLfloat sx = s * x;

	float matrix[16];

	matrix[0]  = tx * x + c;
	matrix[1]  = tx * y + sz;
	matrix[2]  = tx * z - sy;
	matrix[3]  = 0;

	matrix[4]  = tx * y - sz;
	matrix[5]  = ty * y + c;
	matrix[6]  = ty * z + sx;
	matrix[7]  = 0;

	matrix[8]  = tx * z + sy;
	matrix[9]  = ty * z - sx;
	matrix[10] = tz * z + c;
	matrix[11] = 0;

	matrix[12] = 0;
	matrix[13] = 0;
	matrix[14] = 0;
	matrix[15] = 1;

	glMultMatrixf(&matrix[0]);
}

void myDrawLetter()
{
glBegin(GL_QUADS);                // Begin drawing the color cube with 6 quads
      // Top face (y = 1.0f)
      // Define vertices in counter-clockwise (CCW) order with normal pointing out
      glColor3f(0.0f, 1.0f, 0.0f);     // Green
      glVertex3f( 1.0f, 1.0f, -1.0f);
      glVertex3f(-1.0f, 1.0f, -1.0f);
      glVertex3f(-1.0f, 1.0f,  1.0f);
      glVertex3f( 1.0f, 1.0f,  1.0f);

      // Bottom face (y = -1.0f)
      glColor3f(1.0f, 0.5f, 0.0f);     // Orange
      glVertex3f( 1.0f, -1.0f,  1.0f);
      glVertex3f(-1.0f, -1.0f,  1.0f);
      glVertex3f(-1.0f, -1.0f, -1.0f);
      glVertex3f( 1.0f, -1.0f, -1.0f);

      // Front face  (z = 1.0f)
      glColor3f(1.0f, 0.0f, 0.0f);     // Red
      glVertex3f( 1.0f,  1.0f, 1.0f);
      glVertex3f(-1.0f,  1.0f, 1.0f);
      glVertex3f(-1.0f, -1.0f, 1.0f);
      glVertex3f( 1.0f, -1.0f, 1.0f);

      // Back face (z = -1.0f)
      glColor3f(1.0f, 1.0f, 0.0f);     // Yellow
      glVertex3f( 1.0f, -1.0f, -1.0f);
      glVertex3f(-1.0f, -1.0f, -1.0f);
      glVertex3f(-1.0f,  1.0f, -1.0f);
      glVertex3f( 1.0f,  1.0f, -1.0f);

      // Left face (x = -1.0f)
      glColor3f(0.0f, 0.0f, 1.0f);     // Blue
      glVertex3f(-1.0f,  1.0f,  1.0f);
      glVertex3f(-1.0f,  1.0f, -1.0f);
      glVertex3f(-1.0f, -1.0f, -1.0f);
      glVertex3f(-1.0f, -1.0f,  1.0f);

      // Right face (x = 1.0f)
      glColor3f(1.0f, 0.0f, 1.0f);     // Magenta
      glVertex3f(1.0f,  1.0f, -1.0f);
      glVertex3f(1.0f,  1.0f,  1.0f);
      glVertex3f(1.0f, -1.0f,  1.0f);
      glVertex3f(1.0f, -1.0f, -1.0f);
   glEnd();  // End of drawing color-cube
}

void renderScene()
{
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	glEnable(GL_DEPTH_TEST);

	glMatrixMode(GL_MODELVIEW);

	glLoadIdentity();
	gluLookAt( 10.0f, 10.0f, 10.0f,
		   0.0f, 0.0f,  0.0f,
		   5.0f, 5.0f,  0.0f);

	myRotatef(angle*10, 0.0f, 1.0f, 0.0f);
	//glRotatef(angle*10, 0.0f, 1.0f, 0.0f);
	myDrawLetter();

	angle+=0.05f;

	glutSwapBuffers();
}

int main(int argc, char **argv)
{
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA);
	glutInitWindowPosition(100,100);
	glutInitWindowSize(400,400);
	glutCreateWindow("Quartenion");

	glutDisplayFunc(renderScene);
	glutReshapeFunc(changeSize);
	glutIdleFunc(renderScene);

	glutMainLoop();

	return 1;
}