/* NURB curve (1-dimension)

Testing whether we really get a quarter circle with the NURBS given in
Rogers and also in Hill, and whether the curve goes outside the convex
hull.

Written by Caroline Geiersbach and Scott D. Anderson
scott.anderson@acm.org
Summer 2003
*/

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

const int order=3; 
const int numPoints = 3;

GLfloat W = sqrt(2)/2;

GLfloat knots[6] = {0,0,0,1,1,1};

GLfloat points[numPoints][4] = {
  {1,0,0,1},
  {W,W,0,W},
  {0,1,0,1}};

void curve2() {
  GLUnurbs* NURBS2=gluNewNurbsRenderer();
  gluNurbsProperty(NURBS2,GLU_DISPLAY_MODE,GLU_FILL);
  glColor3f(1,0,0);                // red
  gluBeginCurve(NURBS2);
  gluNurbsCurve(NURBS2,numPoints+order,knots,4,&points[0][0],order,
                GL_MAP1_VERTEX_4);
  gluEndCurve(NURBS2);
  gluDeleteNurbsRenderer(NURBS2);
}

void display(void) {
    glClearColor(0.7,0.7,0.7,1);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    // since the figure is in the unit square, this should work.
    float margin = 0.2;
    glOrtho(0-margin,1+margin,
            0-margin,1+margin,
            0,1);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
   
    points[1][0] = points[1][1] = points[1][3] = W;

    glLineWidth(3);

    glColor3f(0,1,0);
    glBegin(GL_LINE_STRIP);
    for(int i=0; i<numPoints; i++) {
      glVertex4fv(points[i]);
    }
    glEnd();

    glColor3f(0,0,1);
    glBegin(GL_LINE_STRIP);
    for(float theta=0.0; theta<M_PI_2; theta += 0.1) 
      glVertex2f(cos(theta),sin(theta));
    glEnd();

    curve2();

    glFlush();
    glutSwapBuffers(); 
}

int tmp;

void keys(unsigned char k, int x, int y) {
  if(k=='q') exit(0);
  if(k=='?') printf("W = %f\n",W);
  if(k=='w') {
    char buf[80];
    printf("W = %f; what new value? ",W);
    fgets(buf,sizeof(buf),stdin);
    sscanf(buf,"%f",&W);
    glutPostRedisplay();
  }
}

int main(int argc, char **argv) {
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
  glutInitWindowSize(650, 650);
  glutCreateWindow("NURBS!");
  glutDisplayFunc(display);
  glutKeyboardFunc(keys);
  if(argc>1) {
    printf("enabling map1 vertex4\n");
    glEnable(GL_MAP1_VERTEX_4);
  }
  glutMainLoop();
  return 0;
}