Hi Andras,

Is it something you plan on fixing for the release ?

Jc

In 4.7 I only plan to add saving of the coordinate space name (hardcoded to RAS).

In the next major release we can change Slicer to save in LPS by default. In a few years we can change Slicer to read as LPS by default (if no coordinate space is specified in the file) - by then there should not be too many legacy files around.

Partial fix is implemented in https://github.com/Slicer/Slicer/pull/798

Discussion on github:

pieper:

Steps 1 and 2 make a lot of sense and there's no reason not to do that.
Steps 3 and 4 sound risky to me, but if there's no better alternative that can be the default plan.
What I'd much rather see that if we are changing the default storage of models we pick a completely different format to avoid ambiguities. DICOM surface segmentations could be a good choice but we could see if there are others that would make more sense. We could maintain VTK export, with the SPACE declaration, as a backwards compatibility mode along with STL and OBJ.

lassoan:

Yes, step 3 and 4 may cause troubles so probably a few year transition time is preferable.
I agree that it would be nice to go towards using DICOM as a primary format for saving data, and in general save everything into DICOM. Currently, saving is mixed with exporting, so it is all somewhat complicated and error-prone, but hopefully we can separate them a bit better in the coming years.

Merged in r26398. Future steps will be discussed in https://issues.slicer.org/view.php?id=4445

• I'd like to do step 2 in vtk.js STL Parser to be able to read files saved from Slicer with SPACE=RAS and properly orient them in LPS space. Could you provide some tips on how to read that field from a binary STL file?
• Any timetable for when step 2 will be implemented in Slicer? I tried replacing RAS by LPS in a saved file and load it in Slicer, and it still loads it as RAS.

It looks like current VTK STL reader cannot read the comment field. It should be easy to add, as if the files starts with "solid" then it is an ASCII file and you just need to read till the end of the line to get the comment field. If it does not start with "solid" then you read the 80-character header that contains the comment. See details here: https://en.wikipedia.org/wiki/STL_%28file_format%29

Any timetable for when step 2 will be implemented in Slicer? I tried replacing RAS by LPS in a saved file and load it in Slicer, and it still loads it as RAS.

After the STL reader is capable of reading the comment field, it can be done very quickly. If you take care of the vtkSTLReader then I can implement Slicer part (ability to read/write as LPS/RAS).

Alexis, I've implemented the necessary changes in VTK:
https://gitlab.kitware.com/vtk/vtk/merge_requests/4084

I would appreciate if you could help facilitating review and integration of the changes.