Add option to import/export snapshot as matrix

[EDCarman]

📝 Description of the feature

Add option to import/export snapshot as matrix

An obstacle to quick adoption of TBROMs in a workflow is the need for the user to create additional functions to convert data in tabular format (generally the most common import/export format from other 3D tools) to snapshot vectors and vice versa.
On the input side, there is the potential error of using column-major, rather than row-major vectorisation, while for outputs, the dimensionality is not directly inferable from the vector and needs to retrieve from the TBROM settings anyway.

e.g. n x 3 matrix must be flattened to 3n vector on input. On output, dimensionality must be retrieved from tbrom.field_output_dim and then used to reshape the vector

x	y	z
x_1	y_1	z_1
x_2	y_2	z_2
...	...	...
x_n	y_n	z_n

flattens to

x_1
y_1
...
z_n

Incorporating these functions simplifies user work and abstracts the snapshot format.

💡 Steps for implementing the feature

A possible option is to provide an additional boolean argument to TbRom.generate_snapshot and TbRom.generate_snapshot to export as a matrix e.g. as_matrix.

Input flattening could use ndarray.flatten(order='C') directly, explicitly using the row-major style. Boolean argument is not strictly necessary, since structure can be inferred from input shape. This would also required the ability to pass inputs in memory (see Issue 107).

Output reshaping can use the numpy.reshape(vec, newshape, order='C') function. New shape columns are retrieved from TBROM field_output_dim, rows calculated from len(vec) / dim.

In both cases, reading/writing matrices to disk need not necessarily be supported. The specific formats required may vary with upstream and downstream programs, so writing can be left to the user.

🔗 Useful links and references

Input matrices would require implementation of Issue #107

[lboucin]

• Implementation size:

btw S & M (depending on if we refactor the static binary data helpers.)

• Priority:

btw low to medium, this is a question that is often raised by ROM users (=> maybe we should document our snapshot data format better in the PyTwin doc?)

[lboucin]

https://numpy.org/doc/stable/reference/generated/numpy.reshape.html