Yay, finally it's (almost) possible to create custom meshes from pure
Python. Except that there always has to be some initial mesh to add
attributes to, and it's not yet possible to supply index data there.
The time saved on not writing those messages back then was really not
worth the time wasted on figuring out what the hell every time one of
these fires.
And yet, somehow Python itself and a ton of libraries raises just an
IndexError alone, with nothing saying *how* wrong it was. Those details,
present in Magnum's own C++ asserts, proved to be extremely valuable for
being able to quickly figure out what's wrong, often even without even
having to look at the code or step through in the debugger.
Also fixes an issue where SceneData.field_object_offset() was rejecting
offsets right at the end of the field. Wasn't caught by tests because
apparently LookupError is a base of IndexError and as there was no
message it just failed elsewhere without being noticed.
Breaking changes, sorry. Also remade the SceneTools hierarchy test to
not be that much redundant -- the name- and ID-based overloads can be
tested together.
These don't copy the data but rather reference the original with
different metadata. That caused use-after-free originally (if the input
variable got deleted or overwritten), the previous commit made it
assert (which was the intention there). Now it works properly.
Vladimír Vondruš