Projection of Circle onto Spherical Surface

\documentclass[border=10pt]{standalone}
\usepackage[inline]{asymptote}
\begin{document}
\begin{asy}[width=\the\linewidth,inline=true]
import graph3;
currentprojection=orthographic(-5,-4,2,center=true);

guide3 sphere_x_cyl(real a, real r, real R, int n=10){
// return a closed curve of the Sphere–cylinder intersection (top part)
// only for the case when a cylinder is completely inside
// except  special case when the x-shift a=0
  assert(a>0,"***** Positive a expected.");

  real b=(R^2-r^2-a^2)/(2a);  
  guide3 g;
  int n=30;
  real phi, dphi;

  phi=0;
  dphi=360/n;

  triple t;
  for(int i=0;i
Source: TeX.SE
Author: g.kov (License)

See also: Original Source