include stdlib include stdio include ctype include math include glut i

#include <stdlib.h>
#include <stdio.h>
#include <ctype.h>
#include <math.h>
#include "glut.h"
#include <vector>
#include <iostream>

using namespace std;

GLUnurbsObj* nobj;
GLfloat ctlarray[][3] = { { -0.9, -0.8, 0.0 },
                          { -0.2, 0.8, 0.0 },
                          { 0.2, -0.5, 0.0 },
                          { 0.9, 0.8, 0.0 } };
GLfloat knot[60];
int degree = 3;
int pointCount = 4;
int knotSize = 0;

void Init() {
  glClearColor(1.0, 1.0, 1.0, 1.0);
  nobj = gluNewNurbsRenderer();
  gluNurbsProperty(nobj, GLU_SAMPLING_TOLERANCE, 25.0);
}

void generateKnot() {
  int k = degree + 1;
  int n = pointCount - 1;
  for (int i = 0; i < n + k + 1; ++i) {
    if (i < k)
      knot[i] = 0;
    else if (i < n + 1)
      knot[i] = i - k + 1;
    else
      knot[i] = n - k + 2;
  }
  knotSize = n + k + 1;
}

void Display() {
  glClear(GL_COLOR_BUFFER_BIT);
  glLineWidth(3.0);
  for (int i = 0; i < 4; ++i) {
    degree = i;
    generateKnot();
    glColor3f(3. / (i + 1), 2. / (i + 1), 1. / (i + 1));
    gluNurbsCurve(nobj, knotSize, knot, 3, &ctlarray[0][0], degree + 1, GL_MAP1_VERTEX_3);
  }
  glPointSize(4.0);
  glColor3f(0.0, 0.0, 1.0);

  glBegin(GL_POINTS);
  for (int i = 0; i < 4; ++i) {
    glVertex3fv(ctlarray[i]);
  }
  glEnd();
  glFlush();
}



int main(int argc, char **argv)
{
  glutInitDisplayMode(GLUT_RGBA | GLUT_SINGLE);
  glutInitWindowSize(1024, 720);
  glutInitWindowPosition(100, 100);
  glutCreateWindow("olol");
  Init();

  glutDisplayFunc(Display);
  glutMainLoop();

  return 0;             /* ANSI C requires main to return int. */
}