#include <GL/openglut.h>
#include <stdlib.h>
GLfloat ctlpoints[4][4][3];
int showPoints = 0;
GLUnurbsObj *theNurb;
void init_surface(void)
{
    int u, v;
    for (u = 0; u < 4; u++) {
    for (v = 0; v < 4; v++) {
        ctlpoints[u][v][0] = 2.0*((GLfloat)u - 1.5);
        ctlpoints[u][v][1] = 2.0*((GLfloat)v - 1.5);
        if ( (u == 1 || u == 2) && (v == 1 || v == 2))
        ctlpoints[u][v][2] = 7.0;
        else
        ctlpoints[u][v][2] = -3.0;
    }
    }
}
void myinit(void)
{
    GLfloat mat_diffuse[] = { 0.7, 0.7, 0.7, 1.0 };
    GLfloat mat_specular[] = { 1.0, 1.0, 1.0, 1.0 };
    GLfloat mat_shininess[] = { 100.0 };
    glClearColor (0.0, 0.0, 0.0, 1.0);
    glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_diffuse);
    glMaterialfv(GL_FRONT, GL_SPECULAR, mat_specular);
    glMaterialfv(GL_FRONT, GL_SHININESS, mat_shininess);
    glEnable(GL_LIGHTING);
    glEnable(GL_LIGHT0);
    glDepthFunc(GL_LESS);
    glEnable(GL_DEPTH_TEST);
    glEnable(GL_AUTO_NORMAL);
    glEnable(GL_NORMALIZE);
    init_surface();
    theNurb = gluNewNurbsRenderer();
    gluNurbsProperty(theNurb, GLU_SAMPLING_TOLERANCE, 25.0);
    gluNurbsProperty(theNurb, GLU_DISPLAY_MODE, GLU_FILL);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    glTranslatef (0.0, 0.0, -5.0);
}
void display(void)
{
    GLfloat knots[8] = {0.0, 0.0, 0.0, 0.0, 1.0, 1.0, 1.0, 1.0};
    int i, j;
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glPushMatrix();
    glRotatef(330.0, 1.,0.,0.);
    glScalef (0.25, 0.25, 0.25);
    gluBeginSurface(theNurb);
    gluNurbsSurface(theNurb,
        8, knots,
        8, knots,
        4 * 3,
        3,
        &ctlpoints[0][0][0],
        4, 4,
        GL_MAP2_VERTEX_3);
    gluEndSurface(theNurb);
    if(showPoints) {
    glPointSize(5.0);
    glDisable(GL_LIGHTING);
    glColor3f(1.0, 1.0, 0.0);
    glBegin(GL_POINTS);
    for(i=0;i<4;i++) {
      for(j=0;j<4;j++) {
    glVertex3f(ctlpoints[i][j][0], ctlpoints[i][j][1], ctlpoints[i][j][2]);
      }
    }
    glEnd();
    glEnable(GL_LIGHTING);
    }
    glPopMatrix();
    glutSwapBuffers();
}
void reshape(int w, int h)
{
    glViewport(0, 0, w, h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective (45.0, (GLdouble)w/(GLdouble)h, 3.0, 8.0);
    glMatrixMode(GL_MODELVIEW);
}
void
menu(int value)
{
    switch (value) {
    case 0:
    case 1:
        showPoints = value;
    break;
    case 2:
        gluNurbsProperty(theNurb, GLU_DISPLAY_MODE, GLU_FILL);
    break;
    case 3:
        gluNurbsProperty(theNurb, GLU_DISPLAY_MODE, GLU_OUTLINE_POLYGON);
    break;
    }
    glutPostRedisplay();
}
int down = 0, lastx;
void
motion(int x, int y)
{
    if (down) {
        glRotatef(lastx - x, 0, 1, 0);
        lastx = x;
        glutPostRedisplay();
    }
}
void
mouse(int button, int state, int x, int y)
{
    if (button == GLUT_LEFT_BUTTON) {
        if (state == GLUT_DOWN) {
            lastx = x;
            down = 1;
        } else {
            down = 0;
        }
    }
}
static void
key(unsigned char k, int x, int y)
{
  switch (k) {
  case 27:  
    exit(0);
    break;
  default:
    return;
  }
  glutPostRedisplay();
}
int
main(int argc, char** argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGB);
    glutCreateWindow(argv[0]);
    myinit();
    glutReshapeFunc(reshape);
    glutDisplayFunc(display);
    glutCreateMenu(menu);
    glutAddMenuEntry("Show control points", 1);
    glutAddMenuEntry("Hide control points", 0);
    glutAddMenuEntry("Solid", 2);
    glutAddMenuEntry("Wireframe", 3);
    glutAttachMenu(GLUT_RIGHT_BUTTON);
    glutMouseFunc(mouse);
    glutMotionFunc(motion);
    glutKeyboardFunc(key);
    glutMainLoop();
    return 0;             
}