Ian Thomas wrote:
> Hello all,
>
> Attached is a patch file against svn head to add triangular grid
> plotting and contouring. It will need some serious checking/reviewing
> before it can be added to MPL. I've tested it on 32 and 64-bit Linux,
> but I don't use other operating systems very often.
>
> Most of the new code is in a new directory lib/matplotlib/tri. There
> is a Triangulation class to store an unstructured triangular grid for
> reuse; the user can either specify the triangles or allow
> matplotlib.delaunay to create a Delaunay triangulation. There are
> three plotting functions: triplot to plot grid lines and points,
> tripcolor to draw a pseudoplot, and tricontour/tricontourf to
> calculate and draw contour lines and filled contours. You can either
> pass in a Triangulation object to these functions, or pass in the x,y
> points, etc and have MPL create a temporary Triangulation for you (for
> convenience).
>
> The underlying contouring code is C++, and I've used CXX to access it.
>
> There are some changes to axes.py and pyplot.py to expose the new
> functionality, and changes to the build scripts to build the new C++
> module. I've also changed contour.py, splitting the previous
> ContourSet class into ContourSet and a derived QuadContourSet so there
> is separate responsibility for creating contours (QuadContourSet) and
> storage/display (ContourSet). ContourSet allows you to specify your
> own polygons to draw, which should allow easier extension to other
> contouring algorithms. QuadContourSet is now used by contour/contourf
> to create contour lines/polygons for a quad grid and the base class
> stores and draws them. The benefit of this approach is that
> QuadContourSet is a relatively small class, allowing the equivalent
> triangular grid contouring class TriContourSet to be similarly small,
> and there is little code duplication.
>
> I've added examples to demonstrate the new functionality, including
> manually creating your own contours, and also a comparison between
> griddata and tricontourf to contour unstructured grids.
>
> Both the C++ and python are documented, but as I'm not familiar with
> the relationship between pydoc strings and sphinx, you may need to
> guide me further to increase/reduce links between and duplication of
> pydocs.
>
> All questions and comments gratefully received.
> Ian
Ian,
I've only glanced so far, but one thing that caught my eye is your
documentation changes and code regarding the need for simply-connected
paths. This is obsolete--mpl now handles multiply-connected paths. If
you look in cntr.c, you will find a "reorder()" function which converts
the simply-connected paths to multiply-connected paths, which render
better, because they don't have the cuts. (Maybe the core routines in
cntr.c could be modified so that the multiply-connected paths would be
generated directly, so that reorder() would not be needed; but I find
those routines very difficult to follow, so writing reorder() was easier.)
A second initial suggestion is that you divide the work into two
patches, one of which provides the refactoring of existing code
(presumably only in contour.py), and a second which adds the new
functionality. This would make reviewing and debugging easier. (Your
contour_manual.py could also go in the first patch.)
Thanks for all the good work!
Eric
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