Re: [Plplot-devel] Problem with filling a clipped polygon

[<mj...@ga...>]

Alan W. Irwin writes:
 > I confirm the bug with latest cvs version on my Debian testing platform.
 > Here is how I would summarize it.  If all the polyline is inside the
 > viewport all is well and the same if all the polyline is outside the
 > viewport.  (The entire viewport is filled if you use plwind(108., 109.0,
 > 108., 109.); below.) But there are problems (the outside of the polyline is
 > filled rather than the inside) if part of the polyline is outside and part
 > inside the viewport.  Note, that when a polyline is clipped at the boundary
 > there are two choices for how it is reconnected. You can connect it the
 > short way along the viewport boundary or the long way around the viewport
 > boundary. For the example below the incorrect "short way" choice was made so
 > that the fill occurred on the wrong side of the clipped polyline.  So I
 > think I know exactly what the problem is, but I have no idea where in the
 > code these viewport boundary/polyline clipping decisions are made.  Could
 > somebody who knows where those decisions are made have a look to see if my
 > hypothesis is correct?

That would be in plP_plfclp(), starting line 618 of src/plline.c.  Lots of
very painstakingly worked out logic, apparently still incomplete.  No
surprise, it's a very tough problem.  Have fun. :)

-- 
Maurice LeBrun    mj...@ga...