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

GLfloat ctrlpoints[4][4][3] = {
   {{-1.5, -1.5,  4.0}, {-0.5, -1.5,  2.0}, {0.5, -1.5, -1.0}, {1.5, -1.5,  2.0}}, 
   {{-1.5, -0.5,  1.0}, {-0.5, -0.5,  3.0}, {0.5, -0.5,  0.0}, {1.5, -0.5, -1.0}}, 
   {{-1.5,  0.5,  4.0}, {-0.5,  0.5,  0.0}, {0.5,  0.5,  3.0}, {1.5,  0.5,  4.0}}, 
   {{-1.5,  1.5, -2.0}, {-0.5,  1.5, -2.0}, {0.5,  1.5,  0.0}, {1.5,  1.5, -1.0}}
};

void init(void) {
   glClearColor (0.0, 0.0, 0.0, 0.0);
   glMap2f(GL_MAP2_VERTEX_3, 0, 1, 3, 4, 0, 1, 12, 4, &ctrlpoints[0][0][0]);
   glEnable(GL_MAP2_VERTEX_3);
   glMatrixMode(GL_PROJECTION); 
   glLoadIdentity();
   glOrtho(-8.0, 8.0, -6.0, 6.0, -5.0, 5.0);
   glMatrixMode(GL_MODELVIEW); 
}
void display(void) {
   int i, j;
   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
   glColor3f(1.0, 1.0, 1.0);
   glLoadIdentity();
   glRotatef(60.0, 1.0, 1.0, 1.0);
   for (j = 0; j <= 8; j++) {
      glBegin(GL_LINE_STRIP);
        for (i = 0; i <= 30; i++) glEvalCoord2f((GLfloat)i/30.0, (GLfloat)j/8.0);
      glEnd();
      glBegin(GL_LINE_STRIP);
        for (i = 0; i <= 30; i++) glEvalCoord2f((GLfloat)j/8.0, (GLfloat)i/30.0);
      glEnd();
   }
   glFlush();
}


int main(int argc, char** argv) {
   glutInit(&argc, argv);
   glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH);
   glutInitWindowSize (800, 600); 
   glutInitWindowPosition (112, 84);
   glutCreateWindow ("bezier-surface"); 
   init ();
   glutDisplayFunc(display);
   glutMainLoop();
   return 0;
}