Merge pull request #347 from jgray-19/subelm_fixes

Thick sub-element fix

Author: ldeniau

src/madl_etrck.mad

@@ -445,7 +445,8 @@ local function tracksub (elm, m, inter, thick, thin, fringe)
   else -- backtrack
     local at, lw = 1
     for i=#elm,1,-1 do
-      at, lw = elm[i].sat, at - elm[i].sat
+      local sat = elm[i].sat - elm[i].l/m.el                                  -- Thick element, therefore at is the exit point (el is weighted by sdir)
+      at, lw = sat, at - sat
       if abs(lw) >= minlen then -- body step
         inter(elm, m, lw, thick, thin)
       end