/*
 *  nurbs.c
 *  This program shows a NURBS (Non-uniform rational B-splines)
 *  surface, shaped like a heart.
 *        (Ting, adpated from the redbook, 25/03/05)
 */
#include <stdio.h>
#include <stdlib.h>
#include <GL/glut.h>

#ifndef WIN32
#define CALLBACK
#endif

#define S_NUMPOINTS 13
#define S_ORDER     3
#define S_NUMKNOTS  (S_NUMPOINTS + S_ORDER)
#define T_NUMPOINTS 3
#define T_ORDER     3
#define T_NUMKNOTS  (T_NUMPOINTS + T_ORDER)
#define SQRT2    1.41421356237309504880

GLenum expectedError;

/* initialized local data */

GLfloat sknots[S_NUMKNOTS] =
    {-1.0, -1.0, -1.0, 0.0, 1.0, 2.0, 3.0, 4.0,
      4.0,  5.0,  6.0, 7.0, 8.0, 9.0, 9.0, 9.0};
GLfloat tknots[T_NUMKNOTS] = {1.0, 1.0, 1.0, 2.0, 2.0, 2.0};

GLfloat ctlpoints[S_NUMPOINTS][T_NUMPOINTS][4] = {
{   {4.,2.,2.,1.},{4.,1.6,2.5,1.},{4.,2.,3.0,1.}    },
{   {5.,4.,2.,1.},{5.,4.,2.5,1.},{5.,4.,3.0,1.} },
{   {6.,5.,2.,1.},{6.,5.,2.5,1.},{6.,5.,3.0,1.} },
{   {SQRT2*6.,SQRT2*6.,SQRT2*2.,SQRT2},
    {SQRT2*6.,SQRT2*6.,SQRT2*2.5,SQRT2},
    {SQRT2*6.,SQRT2*6.,SQRT2*3.0,SQRT2}  },
{   {5.2,6.7,2.,1.},{5.2,6.7,2.5,1.},{5.2,6.7,3.0,1.}   },
{   {SQRT2*4.,SQRT2*6.,SQRT2*2.,SQRT2},
    {SQRT2*4.,SQRT2*6.,SQRT2*2.5,SQRT2},
    {SQRT2*4.,SQRT2*6.,SQRT2*3.0,SQRT2}  },
{   {4.,5.2,2.,1.},{4.,4.6,2.5,1.},{4.,5.2,3.0,1.}  },
{   {SQRT2*4.,SQRT2*6.,SQRT2*2.,SQRT2},
    {SQRT2*4.,SQRT2*6.,SQRT2*2.5,SQRT2},
    {SQRT2*4.,SQRT2*6.,SQRT2*3.0,SQRT2}  },
{   {2.8,6.7,2.,1.},{2.8,6.7,2.5,1.},{2.8,6.7,3.0,1.}   },
{   {SQRT2*2.,SQRT2*6.,SQRT2*2.,SQRT2},
    {SQRT2*2.,SQRT2*6.,SQRT2*2.5,SQRT2},
    {SQRT2*2.,SQRT2*6.,SQRT2*3.0,SQRT2}  },
{   {2.,5.,2.,1.},{2.,5.,2.5,1.},{2.,5.,3.0,1.} },
{   {3.,4.,2.,1.},{3.,4.,2.5,1.},{3.,4.,3.0,1.} },
{   {4.,2.,2.,1.},{4.,1.6,2.5,1.},{4.,2.,3.0,1.}    }
};

GLUnurbsObj *theNurb, *theNurbCurve;

/* Error Callback */

static void CALLBACK ErrorCallback(GLenum which)
{

    if (which != expectedError) {
	fprintf(stderr, "Unexpected error occured (%d):\n", which);
	fprintf(stderr, "    %s\n", gluErrorString(which));
    }
}

/*  Initialize the properties of the nurbs curves and surfaces
 */

void init(void)
{
    theNurb = gluNewNurbsRenderer();

    gluNurbsCallback(theNurb, GLU_ERROR, ErrorCallback);
    gluNurbsProperty(theNurb, GLU_SAMPLING_TOLERANCE, 25.0);
    gluNurbsProperty(theNurb, GLU_DISPLAY_MODE, GLU_OUTLINE_POLYGON);

    theNurbCurve = gluNewNurbsRenderer();
    gluNurbsCallback(theNurbCurve, GLU_ERROR, ErrorCallback);
    gluNurbsProperty(theNurbCurve, GLU_SAMPLING_TOLERANCE, 50.0);

    expectedError = 0;
}

void display(void)
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glPushMatrix();
    glTranslatef (4., 4.5, 2.5);
    glRotatef (220.0, 1., 0., 0.);
    glRotatef (115.0, 0., 1., 0.);
    glTranslatef (-4., -4.5, -2.5);

    /* draw the tesselated surface */
    draw_nurbs_surface();

    /* draw the two border curves */
    draw_nurbs_curve(0);
    draw_nurbs_curve(2);

    glPopMatrix();
    glFlush();
}

int draw_nurbs_surface (void)
{
    /* draw a nurbs tesselated surface */
    glColor3f(1.0,1.0,1.0);    /* white */
    gluBeginSurface(theNurb);
    gluNurbsSurface(theNurb,
	    S_NUMKNOTS, sknots,
	    T_NUMKNOTS, tknots,
	    4 * T_NUMPOINTS,
	    4,
	    &ctlpoints[0][0][0],
	    S_ORDER, T_ORDER,
	    GL_MAP2_VERTEX_4);
    gluEndSurface(theNurb);

  return 1;
}

int draw_nurbs_curve (int i)
{
    /* draw a nurbs curve */
    glColor3f(1.0,0.0,0.0);    /* red */
    gluBeginCurve(theNurbCurve);
    gluNurbsCurve(theNurbCurve,
	    S_NUMKNOTS, sknots,
	    4 * T_NUMPOINTS,
	    &ctlpoints[0][i][0],
	    S_ORDER,
	    GL_MAP1_VERTEX_4);
    gluEndCurve(theNurbCurve);
  return 1;
}

void myReshape(int w, int h)
{
    glViewport(0, 0, w, h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glFrustum(-1.0, 1.0, -1.5, 0.5, 0.8, 10.0);

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    gluLookAt(7.0,4.5,4.0, 4.5,4.5,2.0, 6.0,-3.0,2.0);
}

static void
key(unsigned char k, int x, int y)
{
  switch (k) {
  case 27:  /* Escape */
    exit(0);
    break;
  default:
    return;
  }
  glutPostRedisplay();
}

/*  Main Loop
 *  Open window with initial window size, title bar,
 *  RGBA display mode, and handle input events.
 */
int main(int argc, char** argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH);
    glutCreateWindow (argv[0]);
    init();
    glutReshapeFunc (myReshape);
    glutDisplayFunc(display);
    glutKeyboardFunc(key);
    glutMainLoop();
    return 0;             /* ANSI C requires main to return int. */
}