How do I?

[mydana]

So far this library looks really cool.
Perhaps I'm missing something really obvious but there are two actions I don't see in the documentation.

How do I create and save a new stl file?

How do I extend or reduce the mesh for an existing mesh object?

[wolph]

Thanks, you're right that they're missing from the documentation. I'll put them on the todo to add :)
(they're in #5 and #6). I've updated the docs a bit already, apparently readthedocs didn't work correctly before: http://numpy-stl.readthedocs.org/en/latest/stl.html

Creating a new STL file from scratch is a bit tricky right now, mainly because this library was initially written for the purpose of reading and modifying existing STL files. I'll modify that in a future version, for now there's only a hack available.

Here's the current way to create a new StlMesh object:

from stl.mesh import Mesh
from stl.stl import StlMesh

VERTICE_COUNT = 100
data = numpy.zeros(VERTICE_COUNT, dtype=Mesh.dtype)
mesh = Mesh(data, remove_empty_areas=False)

# And to convert that to an STL object (NOTE THAT THIS IS NOT RECOMMENDED):
stl_mesh = StlMesh.__new__(StlMesh)
Mesh.__init__(stl_mesh, mesh.data)

Where VERTICE_COUNT is the amount of vertices you are going to use.

This is a hack to work around the current limitations as it wasn't designed with this purpose in mind, I can easily modify this in a future version but I would need a bit of info about how you plan to use the library :)

Extending or reducing the mesh currently uses a similar process, the library is designed to take an existing mesh and rotate/translate/scale/etc. that mesh. If you want to extend/reduce it a new object would have to be created since the numpy storage used in the background doesn't have the features to shrink/grow either.

Can you tell me how you plan to use the library? I can probably add the features you need easily :)

[mydana]

I'm looking to experiment with 3-D printing, and want to use this library to create STL files that will be sent to a service bureau to have printed.

For my use case it's easy enough to pre-compute the number of vertices, so extending and reducing isn't that important.

As to saving a file, perhaps consider moving the save methods to the Mesh base class, possibly with a wrapper in the StlMesh class. This will allow saving of meshes that are created new and those that are loaded from files.

[wolph]

I've just created a new release which supports creating a new mesh and saving it to file by using a common base class. This should provide enough extensibility for the future while still keeping the code separate :)

Please give it a try and see if it works for you