/* 
 * Animated Cube with 3 planes meeting in a corner. 
 * compile with g++-4.4 -o cube cube.cc -lGL -lGLU -lglut 
 */
#include <GL/gl.h>
#include <GL/glut.h>
#include <math.h>
#include <unistd.h>

int angle = -10;
int step = 1;
double axis[3] = {1.0, 0.0, 0.0};

void display () {
  int i;
  GLfloat c[3] = {0,1,0};
  float l = 1;
  float d = l*sqrt(2);
  /* clear window */
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  glMatrixMode(GL_MODELVIEW);
  /* a white cube */
  glPushMatrix();
  glRotatef(angle,1,0.8,0);
  glColor4f(1,1,1,1);
  glutWireCube(2*l);
  /* three diagonal planes */
  glPushMatrix();
  glRotatef(45,1,0,0);
  for (i = 0; i < 3; i++) {
    glColor4f(c[i],c[(i+1)%3],c[(i+2)%3],.6);
    glRectf(-l, d, l, -d);
    glRotatef(120,l,d,0);
  }
  glPopMatrix();
  glPopMatrix();
  /* flush drawing routines to the window */
  glFlush();
  glutSwapBuffers();
}

void reshape ( int width, int height ) {
  /* define the viewport transformation */
  glViewport(0, 0, width, height);
}

void animate () {
  angle += step;
  if (abs(angle) == 30 ) {
    step *= -1;
  }
  sleep(1);
  glutPostRedisplay();
}

int main ( int argc, char ** argv ) {
  /* initialize GLUT, using any commandline parameters passed to the 
     program */
  glutInit(&argc,argv);

  /* setup the size, position, and display mode for new windows */
  glutInitWindowSize(400, 400);
  glutInitWindowPosition(0, 0);
  glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE | GLUT_DEPTH);

  /* create and set up a window */
  glutCreateWindow("D6 at cube corner");
  glutDisplayFunc(display);   /* register function that draws the objects */
  glutReshapeFunc(reshape);   /* register function handling resizing */
  glutIdleFunc(animate);

  glEnable(GL_DEPTH_TEST);
  glEnable(GL_BLEND);
  glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

  /* define the projection transformation */
  glMatrixMode(GL_PROJECTION);   /* choose projection matrix stack */
  glLoadIdentity();              /* set it to the identity matrix */
  gluPerspective(60,1,0.1, 6.0);   /* an orthogonal parallel projection 
					 * left, right, bottom, top, zNear,
					 * and zFar */
  
  /* define the viewing transformation */
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
  gluLookAt(3.0, 1.6, 2.0,    /* eye*/
	    0.0, 0.0, 0.0,     /* point to look at */
	    0.0, 1.0, 0.0);    /* up direction */

  /* tell GLUT to wait for events */
  glutMainLoop();
}