title: Create contour from Intersecting of triangle mesh and plane
body: <p>i have problem with creating contour.</p>
  
  <p>I have an STL file, the STL file includes many facets,by intersecting facets with cutting plane<code>(Z=dz,x=y=0)</code>, we have an array of lines at each incremental Z.</p>
  
  <p>However lines are not in order.I want to sort and connect them to form closed contour or continuous path. Please help me with a program or code to solve this problem.</p>