[Numpy-discussion] Re: numpy and mayavi

[Bryan C. <br...@co...>]

On Sat, 2006-05-20 at 22:57 +0200, Emanuele Olivetti wrote:
> I need to use a 3D visualization toolkit together with the
> amazing numpy. On the scipy website mayavi/VTK are suggested but
> as far as I tried, mayavi uses only Numeric and doesn't like
> numpy arrays (and mayavi, last release, dates 13 September 2005
> so a bit earlier for numpy).

You can safely install Numeric along side numpy; you'll need to do this
in order to run mayavi. Alternatively, you could try Paraview
(http://www.paraview.org). Like mayavi, Paraview is based on VTK, but
it's written in Tcl/Tk rather than python. It's more feature complete
than mayavi and easier to use, in my view.

I quick test shows that VTK-5 is happy to accept numpy arrays as "Void
Pointers" for its vtkDataArrays. Using this method, you can construct
any vtkDataObject from numpy arrays. If you just want to turn your 3D
array into vtkImageData, you can use the vtkImageImport filter. 

Once you've got a vtkDataSet (vtkImageData or some other form), you can
save this as a .vtk file, which either mayavi or paraview can then open.

If you're not already familiar with VTK programming, then another way to
get going is to convert your numpy array directly to a VTK data file
using a pure python script. The file formats are documented at
http://www.vtk.org/pdf/file-formats.pdf and the can be written in either
binary or ascii form. The 'legacy' .vtk formats and are quite simple to
construct. 

If you want to use mayavi from a script, then you need to convert your
numpy arrays to Numeric arrays (using the Numeric.asarray function) for
transfer to mayavi as needed.

HTH
Bryan

>  Do you know something about it or
> could suggest alternative 3D visualization packages?
> Basically my needs are related to this task: I've 3D matrices
> and I'like to see them not only as 2D slices.
> 
> Thanks in advance,
> 
> Emanuele
> 
> 
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