/* rotating cube with color interpolation */

/* demonstration of use of homogeneous-coordinate transformations
and simple data structure for representing cube from Chapter 4 */
/* colors are assigned to the vertices */
/* cube is centered at origin */

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


GLfloat vertices[] ={-1.0,-1.0,-1.0,1.0,-1.0,-1.0,
1.0,1.0,-1.0, -1.0,1.0,-1.0, -1.0,-1.0,1.0, 1.0,-1.0,1.0,
1.0,1.0,1.0, -1.0,1.0,1.0};

GLfloat colors[] = {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};

GLubyte cubeIndices[]={0,3,2,1,2,3,7,6,0,4,7,3,1,2,6,5,4,5,6,7,0,1,5,4};


static GLfloat theta[] = {0.0,0.0,0.0};
static GLint axis = 2;

void display()
{
/* 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);

 glDrawElements(GL_QUADS, 24, GL_UNSIGNED_BYTE, cubeIndices);

 glBegin(GL_LINES);
   glVertex3f(0.0,0.0,0.0);
   glVertex3f(1.0,1.0,1.0);
 glEnd();
 glFlush();
 glutSwapBuffers();
}

void spinCube()
{

/* idle callback, spin cube 2 degrees about selected axis */

 theta[axis] += 2.0;
 if( theta[axis] > 360.0 ) theta[axis] -= 360.0;
 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)
{

/* need both double buffering and z buffer */

   glutInit(&argc, argv);
   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 */
   glEnableClientState(GL_COLOR_ARRAY);
   glEnableClientState(GL_NORMAL_ARRAY);
   glEnableClientState(GL_VERTEX_ARRAY);
   glVertexPointer(3, GL_FLOAT, 0, vertices);
   glColorPointer(3,GL_FLOAT, 0, colors);
   glColor3f(1.0,1.0,1.0);
   glutMainLoop();
}
