/* -*-ePiX-*- */
#include "epix.h"
using namespace ePiX;

const double ht(0.6);
const double k(5); // tightness of bending

P E(0, ht), ptP2(4.5, ht), Sun(1.5, 0.3);

double f(double t)
{
  t -= Sun.x1();
  return log(1 + exp(k*t))/k;
}

P straight(double t)
{
  return E + t*(ptP2 - E);
}

P bent(double t)
{
  P tmp(straight(t));
  double tau(tmp.x1());
  return tmp - P(0, 0.15*f(tau));
}

int main()
{
  picture(P(0,0), P(4.5,1), "4.5 x 1in");

  begin();

  label(P(0.5*(xmin()+xmax()), ymin()), P(0,-8), "\\textsc{Fig.~16.}", b);

  bold();
  circle(Sun, 0.125);
  plot(bent, 0, 1, 60);

  dashed();
  line(E, ptP2);

  font_size("footnotesize");
  label(Sun, "$S$");

  dot(E, P(2,2), "$E$", tr);
  label(straight(0.25), P(0,2), "$F$", t);

  label(straight(1), P(0,2), "$P'$", t);

  label(bent(0.5), P(0,-2), "$Q$", b);
  label(bent(1), P(0,2), "$P$", t);

  tikz_format();
  end();
}