[SciPy-User] [SciPy-user] set difference on meshes

[Gael Varoquaux]

On Mon, Aug 17, 2009 at 08:03:10PM -0700, Martin van Leeuwen wrote:
> http://code.enthought.com/projects/mayavi/docs/development/html/mayavi/mlab.html

> , under: "From data points to surfaces." But I don't see how
> delaunay2d() needs to be implemented to return the trianges that
> triangular_mesh() needs.

It doesn't. It returns a data structure on which you can apply the
surface module, amongst other things, with:

mlab.pipeline.surface(obj)

where obj is returned by mlab.pipeline.delaunay2d.

You can also get the data as arrays as in the following:

In [1]: from enthought.mayavi import mlab

In [2]: import numpy as np

In [3]: x, y, z, s = np.random.random((4, 10))

In [4]: src = mlab.pipeline.scalar_scatter(x, y, z, s)

In [5]: mesh = mlab.pipeline.delaunay2d(src)

In [6]: surf = mlab.pipeline.surface(mesh)

In [7]: mesh.outputs[0].polys.to_array()
Out[7]: 
array([3, 9, 4, 3, 3, 5, 3, 2, 3, 8, 7, 0, 3, 6, 3, 1, 3, 4, 2, 3, 3, 5, 1,
       3, 3, 6, 1, 0, 3, 7, 3, 6, 3, 7, 6, 0, 3, 9, 3, 8, 3, 8, 3, 7, 3, 9,
       2, 4])

In [8]: mesh.outputs[0].points.to_array()
Out[8]: 
array([[ 0.94464944,  0.47644135,  0.72179666],
       [ 0.74063624,  0.09717904,  0.81146878],
       [ 0.17031379,  0.73111888,  0.62790633],
       [ 0.50215195,  0.54242855,  0.20974343],
       [ 0.27069343,  0.83886682,  0.38808641],
       [ 0.15944449,  0.21834495,  0.39882205],
       [ 0.78877187,  0.34613708,  0.79911974],
       [ 0.86809041,  0.48792871,  0.65521137],
       [ 0.85557844,  0.57255716,  0.6484326 ],
       [ 0.30144246,  0.96996277,  0.15670321]])

In [9]: mesh.outputs[0].point_data.scalars.to_array()
Out[9]: 
array([ 0.18869998,  0.87639289,  0.51392855,  0.30845021,  0.57186958,
        0.74023876,  0.41477073,  0.50683163,  0.4276263 ,  0.80960671])

HTH,

Gaël