Changes to VTK polydata between 4.10 and 4.11

[codey]

I have noticed that VTK meshes imported in 4.10 and 4.11 differ in their spatial location. Rotation by 180 corrects for this. I presume this is down to a different interpretation of the VTK coordinate system. between the slicer versions. Does anyone know why these are different?

[Andinet_Enquobahrie]

This is probably due to the change in 4.11 in the way coordinate system of model files are handled in 3D Slicer

Model files are now saved in LPS coordinate system

While Slicer uses RAS coordinate system internally, images, transforms, and markups files are stored in LPS coordinate system, because DICOM and all medical image computing software (maybe except a few very old ones) uses LPS coordinate system in files. However, Slicer has been still using its internal RAS coordinate system in mesh files (STL, VTK, VTP, OBJ, PLY), which caused issues when interfacing with third-party software. Starting from tomorrow (Slicer-4.11.0-2020-02-26, revision 28794), …