/*  
 
   simple6.c 
   
   draws a cube in 3D 
 
   OpenGL 1.x 
   Laura Toma 
*/ 
 
 
#include <stdlib.h> 
#include <stdio.h> 
#include <math.h> 
#include <assert.h> 
 
#ifdef __APPLE__ 
#include <GLUT/glut.h> 
#else 
#include <GL/glut.h> 
#endif 
 
 
GLfloat red[3] = {1.0, 0.0, 0.0}; 
GLfloat green[3] = {0.0, 1.0, 0.0}; 
GLfloat blue[3] = {0.0, 0.0, 1.0}; 
GLfloat black[3] = {0.0, 0.0, 0.0}; 
GLfloat white[3] = {1.0, 1.0, 1.0}; 
GLfloat gray[3] = {0.5, 0.5, 0.5}; 
GLfloat yellow[3] = {1.0, 1.0, 0.0}; 
GLfloat magenta[3] = {1.0, 0.0, 1.0}; 
GLfloat cyan[3] = {0.0, 1.0, 1.0}; 
 
 
/* forward declarations of functions */ 
void display(void); 
void keypress(unsigned char key, int x, int y); 
 
 
 
//draw [-1,1] x [-1,1] rectangle at specified z  
void draw_xy_rect(GLfloat z, GLfloat r, GLfloat g, GLfloat b) { 
  glBegin(GL_POLYGON); 
  glColor3f(r,g,b); 
  glVertex3f(-1,-1, z); 
  glVertex3f(-1,1, z); 
  glVertex3f(1,1, z); 
  glVertex3f(1,-1, z); 
  glEnd(); 
} 
 
void draw_cube(GLfloat z1, GLfloat z2) { 
  glPolygonMode(GL_FRONT_AND_BACK, GL_LINE); 
 
  //front face at z=z1 with RED 
  draw_xy_rect(z1,1,0,0); 
 
  //back face at z=z2 woth BLUE 
  draw_xy_rect(z2,0,0,1); 
 
  //draw the sides  
  glColor3fv(yellow); 
  glBegin(GL_POLYGON); 
  glVertex3f(-1,-1, z1); 
  glVertex3f(-1,1, z1); 
  glVertex3f(-1,1, z2); 
  glVertex3f(-1,-1, z2); 
  glEnd(); 
 
  glBegin(GL_POLYGON); 
  glColor3fv(cyan); 
  glVertex3f(1,-1, z1); 
  glVertex3f(1,1, z1); 
  glVertex3f(1,1, z2); 
  glVertex3f(1,-1, z2); 
  glEnd(); 
} 
 
 
void keypress(unsigned char key, int x, int y) { 
  switch(key) { 
  case 'q': 
    exit(0); 
    break; 
  } 
} 
 
 
 
void display(void) { 
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); 
 
  //this won't show anything, because it's right on the edge of the 
  //view frustrum and the camera is inside it at (0,0,0) 
  //draw_cube(1, -1);  we need to translate it first
 
  glTranslatef(0,0,-3); 
  draw_cube(1, -1); 
  
  glFlush(); 
} 
 
 
 
int main(int argc, char** argv) { 
 
    /* open a window */ 
  glutInit(&argc, argv); 
  glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH); 
  glutInitWindowSize(500, 500); 
  glutInitWindowPosition(100,100); 
  glutCreateWindow(argv[0]); 
  
  /* OpenGL init */ 
  glClearColor(0, 0, 0, 0);   /* set background color black*/ 
  
  /* initial view */ 
  glMatrixMode(GL_PROJECTION); 
  glLoadIdentity(); 
  gluPerspective(60, 1, 1, 10.0); 
  /* aspect=1; the frustrum is from z=-1 to z=-10 */ 
  /* DEFAULT: camera is at (0,0,0) looking along negative z axis */ 
  glMatrixMode(GL_MODELVIEW); 
 
  
  /* callback functions */ 
  glutDisplayFunc(display); 
  glutKeyboardFunc(keypress); 
  
  /* event handler */ 
  glutMainLoop(); 
  return 0; 
}