#define F_TORUS 1

struct point {
  double p[3];
  double n[3];
};

extern double a, b, c, d, e, f;
extern int ifun;

void quadrilateral (double u0, double u1, double v0, double v1);
void triangle (struct point pa, struct point pb, struct point pc);

void parseargs (int argc, char *argv[]);

void surface (double u, double v, struct point *p);