/* cube.c  Rotating cube with color interpolation */
/* E. Angel, Interactive Computer Graphics */

/* Demonstration of use of homogeneous coordinate */
/* transformations and simple data structure for representing */
/* cube from Chapter 4 */
/* Colors are assigned to the vertices */
/* Mouse buttons control direction of rotation */
#include <stdlib.h>
#include <GL/glut.h>

GLfloat vertices[][3] = {{-1.0,-1.0,-1.0}, { 1.0,-1.0,-1.0}, /* 0,1   */
       { 1.0, 1.0,-1.0}, {-1.0, 1.0,-1.0}, {-1.0,-1.0, 1.0}, /* 2,3,4 */
       { 1.0,-1.0, 1.0}, { 1.0, 1.0, 1.0}, {-1.0, 1.0, 1.0}};/* 5,6,7 */
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}};
static GLfloat theta[] = {0.0,0.0,0.0};
static GLint axis = 2;

void polygon(int a, int b, int c , int d)
{
  /* draw a polygon via list of vertices */
  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 6 faces */
  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, swap buffers */
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  glLoadIdentity();
  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 spinCube(void)
{
  /* Idle callback, spin cube 2 degrees about selected axis */
  theta[axis] = theta[axis] + 2.0;
  if(theta[axis] > 360.0) theta[axis] = theta[axis] - 360.0;
  /* display(); */
  glutPostRedisplay();
}

void mouse(int btn, int state, int x, int y)
{
  /* mouse callback, selects an axis about which to rotate */
  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;
}

void myReshape(int w, int h)
{
  glViewport(0, 0, w, h);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  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);
}

int main(int argc, char *argv[])
{
  glutInit(&argc, argv);
  /* need both double buffering and z buffer */
  glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
  glutInitWindowSize(500, 500);
  glutCreateWindow("colorcube");
  glutReshapeFunc(myReshape);
  glutDisplayFunc(display);

  glutIdleFunc(spinCube);

  glutMouseFunc(mouse);
  glEnable(GL_DEPTH_TEST); /* Enable hidden--surface--removal */
  glutMainLoop();
  return 0;
}