#include <stdio.h>
#include <stdlib.h>
#include <GLUT/glut.h>

/*
 * nonuniform rational B-spline surface
 *
 * 4/7/03 pjf
 *
 */



GLfloat p[4][4][3];

#define NKNOTS 8
GLfloat knots[8] = { 0, 0, 0, 0, 1, 1, 1, 1 };  // open spline aka Bezier curve

#define ORDER 4
#define USTRIDE (4*3)
#define VSTRIDE 3

GLUnurbsObj *nurb;


void init_surface(void) {  // define a "hill"  approacing z=3 in the middle, z=-3 at the edges
 int u,v;
 for(u=0;u<4;u++)
  for(v=0;v<4;v++) {
   p[u][v][0] = 2.0*(u-1.5);
   p[u][v][1] = 2.0*(v-1.5);
   if (((u==1) | (u==2)) && ((v==1)||(v==2))) 
    p[u][v][2] = 3.0;
   else
    p[u][v][2] = -3.0;
   }
 }

void CALLBACK nurbsError(GLenum errorCode) {
 const GLubyte *s = gluErrorString(errorCode);
 fprintf(stderr,"NURBS error: %s\n",s);
 exit(-1);
 }


/* display callback */
void display() {
 int i,j;
 glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
 glPushMatrix();
 glRotatef(330,1,0,0);
 glScalef(.5,.5,.5);

 gluBeginSurface(nurb);
 gluNurbsSurface(nurb,NKNOTS,knots,  // u knots
                      NKNOTS,knots,  // v knots
                      USTRIDE,       //u 
                      VSTRIDE,       //v
                      &p[0][0][0],
                      ORDER, ORDER, GL_MAP2_VERTEX_3);
 gluEndSurface(nurb);

 // display the control points
 glPointSize(5);
 glDisable(GL_LIGHTING);
 glColor3f(1,1,0);
 glBegin(GL_POINTS);
 for(i=0;i<4;i++)
  for(j=0;j<4;j++)
   glVertex3f(p[i][j][0],p[i][j][1],p[i][j][2]);
 glEnd();
 glEnable(GL_LIGHTING);
 
 glPopMatrix();
 glFlush();
 }


void reshape(int w, int h) {
  glViewport(0,0,(GLsizei)w,(GLsizei)h);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  gluPerspective(45,(GLdouble)w/(GLdouble)h,3.0,8.0);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
  glTranslatef(0,0,-5);
 }
  
void init(void) {
 GLfloat diffuse[] = { .7, .7, .7, 1 }, specular[] = { 1, 1, 1, 1 }, shine[] = { 100 };

 glClearColor(0,0,0,0);
 glMaterialfv(GL_FRONT,GL_DIFFUSE,diffuse);
 glMaterialfv(GL_FRONT,GL_SPECULAR,specular);
 glMaterialfv(GL_FRONT,GL_SHININESS,shine);
 glEnable(GL_LIGHTING);
 glEnable(GL_LIGHT0);
 glEnable(GL_DEPTH_TEST);
 glEnable(GL_AUTO_NORMAL);
 glEnable(GL_NORMALIZE);

 init_surface();
 
 nurb = gluNewNurbsRenderer();
 gluNurbsProperty(nurb,GLU_SAMPLING_TOLERANCE,25);
 gluNurbsProperty(nurb,GLU_DISPLAY_MODE,GLU_OUTLINE_POLYGON);
 gluNurbsCallback(nurb,GLU_ERROR,nurbsError);
 }

int main(int argc, char **argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_RGB);
    glutInitWindowSize(500, 500);
    glutCreateWindow(argv[0]);
    glutReshapeFunc(reshape);
    glutDisplayFunc(display);
    init();
    glutMainLoop();
    return 0;
}