These routines allow easy plotting of lines or contours with hatches on one side. This line style is often used to represent a constraint, where one side of the line represents a no-go area.
Theo - Quite correct, that is a bad habit left over from long ago.
Glad this was of use to you.
Very helpful. The only question I had was, in the example.m code, you use "c1=ocontourc(x1,x2',con1',[0 1e6]);" Why [0 1e6]? Should this not be [0 0]? It creates some artifacts near the origin.
Added ocontourc, a version of contourc which always results in consistently oriented contours.
Finally added screenshot to show what this does.