/*
 * Adapted from http://www.opengl.org/resources/code/samples/redbook/surface.c
 * 
 *  Wu Shin - Ting (9/03/10)
 *
 */

/*
 *  curve.c
 *  This program draws a NURBS curve equivalent to a Bezier
 *  curve.
 *  The 'c' keyboard key allows you to 
 *  toggle the visibility of the control points themselves.  
 */

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

#ifndef CALLBACK
#define CALLBACK
#endif

GLfloat ctlpoints[4][3] = {
	{ -4.0, -4.0, 0.0}, { 1.0, 4.5, 0.0},
	{-1.0, 4.5, 0.0}, {4.0, -4.0, 0.0}};

GLfloat knots[8] = {0.0, 0.0, 0.0, 0.0, 1.0, 1.0, 1.0, 1.0};

int showPoints = 1;

GLUnurbsObj *theNurb;
			

void CALLBACK nurbsError(GLenum errorCode)
{
   const GLubyte *estring;

   estring = gluErrorString(errorCode);
   fprintf (stderr, "Nurbs Error: %s\n", estring);
   exit (0);
}
			
/*  Initialize 
 */
void init(void)
{

   glClearColor (0.0, 0.0, 0.0, 0.0);

   theNurb = gluNewNurbsRenderer();
   gluNurbsProperty(theNurb, GLU_SAMPLING_METHOD, GLU_PATH_LENGTH);
   gluNurbsProperty(theNurb, GLU_PARAMETRIC_TOLERANCE, 0.1);
   gluNurbsCallback(theNurb, GLU_ERROR, 
                    nurbsError);
}

void display(void)
{
   int i, j;

   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
   
   glLineWidth(3.0);
   glColor3f(1.0, 1.0, 1.0);
   gluBeginCurve(theNurb);
   gluNurbsCurve(theNurb, 
                   8, knots, 
                   3, &ctlpoints[0][0], 
                   4, GL_MAP1_VERTEX_3);
   gluEndCurve(theNurb);

   if (showPoints) {
      glPointSize(5.0);
      glColor3f(1.0, 1.0, 0.0);
      glBegin(GL_POINTS);
      for (i = 0; i < 4; i++) {
	    glVertex3f(ctlpoints[i][0], 
               ctlpoints[i][1], ctlpoints[i][2]);
      }
      glEnd();
	  
      glLineWidth(1.0);
      glColor3f(1.0, 1.0, 1.0);
      glBegin(GL_LINE_STRIP);
      for (i = 0; i < 4; i++) {
	    glVertex3f(ctlpoints[i][0], 
               ctlpoints[i][1], ctlpoints[i][2]);
      }
      glEnd();
   }

   glFlush();
}

void reshape(int w, int h)
{
   glViewport(0, 0, (GLsizei) w, (GLsizei) h);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   if (w <= h)
      glOrtho(-5.0, 5.0, -5.0*(GLfloat)h/(GLfloat)w, 
               5.0*(GLfloat)h/(GLfloat)w, -5.0, 5.0);
   else
      glOrtho(-5.0*(GLfloat)w/(GLfloat)h, 
               5.0*(GLfloat)w/(GLfloat)h, -5.0, 5.0, -5.0, 5.0);
   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();
}

void keyboard(unsigned char key, int x, int y)
{
   switch (key) {
      case 'c':
      case 'C':
         showPoints = !showPoints;
         glutPostRedisplay();
         break;
      case 27:
         exit(0);
         break;
      default:
         break;
   }
}

int main(int argc, char** argv)
{
   glutInit(&argc, argv);
   glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH);
   glutInitWindowSize (500, 500);
   glutInitWindowPosition (100, 100);
   glutCreateWindow(argv[0]);
   init();
   glutReshapeFunc(reshape);
   glutDisplayFunc(display);
   glutKeyboardFunc (keyboard);
   glutMainLoop();
   return 0; 
}