Re: [Matplotlib-users] matplotlib 3D: equivalent to Matlab patch()?

[Benjamin R. <ben...@ou...>]

On Thu, Sep 29, 2011 at 4:09 AM, Holger Brandsmeier <
hol...@sa...> wrote:

> Dear list,
>
> is there an equivalent function to matlabs patch() function in matplotlib?
>  http://dali.feld.cvut.cz/ucebna/matlab/techdoc/ref/patch.html
> That means a function which does not require its X,Y,Z arguments to
> come from a prior call to meshgrid? That is at least what I believe to
> be the requirement for Axes3DSubplot.plot_surface.
>
> In matlab you can pass n x k matrices as X,Y,Z argument, which then
> means that there are n Polygons (each with k vertices) and they each
> get shaded. The problem with the meshgrid structure is, that an
> unstructured mesh does not have this tensor structure, so if I have
> 1000 quadrilaterals, then I would have to call
> `Axes3DSubplot.plot_surface` for each of them separately. At least
> with `gtkagg` this even seems to fail with z-buffer problem. Btw.
> which backend to you recommend for 3D plots?
>
> -Holger


There are some ways to do what you want.  For some simple examples:

http://matplotlib.sourceforge.net/examples/mplot3d/polys3d_demo.html
http://matplotlib.sourceforge.net/examples/mplot3d/pathpatch3d_demo.html

These examples show how you can take a normal 2D matplotlib patch and
convert it into a 3D object.

Unfortunately, I do not have any example on hand on how to work with the 3D
versions of the objects directly, but that is possible. You can find the
classes in the 'mpl_toolkits.mplot3d.art3d' module. Do keep in mind that
mplot3d is currently only meant for simple 3D plots, as it can not properly
lay out a 3D environment (intersecting polygons, for example will look
Escher-like).  As for backends, the only thing that mplot3d requires is that
it uses an Agg-based backend so that it can perform arbitrary rotation of
text elements (for axes labels).

I hope this helps a bit.
Ben Root