I am modifying some STL files for 3d printing which originated from a GPL'd project, and though the originals are available, the "object code" STLs are easier to modify in my case.
Ignoring the fact that the GPL is questionably applicable to hardware, what are the requirements in general for what to do if one modifies the object code of a GPL program and distributes that? There are all sorts of requirements for what to do with regards to providing source, but what if I don't have source files of the same format as the original to provide?
Another confusion is what occurs if I import the STL (object code) into my computer aided design software, and modify it in that software. Do I need to release the CAD file in native, easily editable form following my edits? (or in a software example, say I disassemble a GPL program in IDA and edit it, do I need to release the IDA database as well as the modified object code?)
In any case, do I need to provide the source code of the upstream project?