#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include "writemesh.h"

void
surface (double u, double v, struct point *p)
{
  double z, ro, ron;
  double bb;
  double sinu, sinv, cosu, cosv, bp, v1, v2, v3, w1, w2, w3;

  switch (ifun)
  {
    case F_TORUS:    /* toro standard */
    z = b*sin(v);
    ron = b*cos(v);
    ro = a + ron;

    p->n[2] = p->p[2] = z;
    p->n[0] = ron*cos(u);
    p->n[1] = ron*sin(u);

    p->p[0] = ro*cos(u);
    p->p[1] = ro*sin(u);
    break;

    case 2:         /* toro con strozzatura */
    sinu = sin(u);
    cosu = cos(u);
    sinv = sin(v);
    cosv = cos(v);

    bb = b - c*sinu;
    z = bb*sinv;
    ro = a + bb*cosv;

    p->p[0] = ro*cosu;
    p->p[1] = ro*sinu;
    p->p[2] = z;

    bp = - c*cosu;
    v1 = bp*cosu*cosv - ro*sinu;
    v2 = bp*sinu*cosv + ro*cosu;
    v3 = bp*sinv;
    w1 = - sinv*cosu;
    w2 = - sinv*sinu;
    w3 = cosv;
    p->n[0] = v2*w3 - v3*w2;
    //ron*cosu;
    p->n[1] = v3*w1 - v1*w3;
    //ron*sinu;
    p->n[2] = v1*w2 - v2*w1;
    //z;
    break;

    default:
    printf ("Invalid ifun choice: %d\n", ifun);
    exit (1);
  }
  return;
}