A somewhat inverse / complementary utility for parentsBreadthFirst() --
while the former is useful mainly for convenient parent referencing,
this is for children and nested children. Currently the main use case is
extracting scene subtrees, which is also what the example snippet shows.
Getting a list of direct children is also possible, although for that
it's possible to use the parentsBreadthFirst() as well as the Parent
field directly, simply by scanning for all field entries with given
value.
This allows to filter individual field entries in the scene, such as
for example removing certain mesh assignments that were collapsed
together. A higher-level API that allows filtering all data belonging to
a certain set of objects will be then implemented on top of this one.
Same reasoning as before, the verb suggests it's transforming the
SceneData in some way, which isn't true, it just retrieves the data in a
certain way. And if an API that actually operates on SceneData got
added, it would be easily confused with this one.
Plus, the "order" isn't just one, this orders objects so they're grouped
with a common parent, but what if I wanted to instead order depth first?
Thus it's explicitly saying this is a breadth-first order.
The API got moved to the Hierarchy.h header, removing a need for a
dedicated file and test.
That's a second deprecation of this API in a short while, sorry. This
variant is hopefully the final one, with the previous one I still had
the problem that it contained a verb, which implied that it'd
*transform* the SceneData in some way which (unlike combineFields(),
filterFields() etc.) it didn't, it just extracts some data in a certain
way. This would all cause problems when there are APIs that actually do
perform hierarchy flattening.
It's also moved to a new, more general Hierarchy.h header which will
contain other hierarchy-related APIs. It doesn't make sense to have a
tiny header with just a single function, especially given it doesn't
depend on any heavy headers on its own.
Besides that it also makes the UnsignedInt overloads the main ones, and
the Trade::SceneField secondary, as is already done everywhere else (and
the opposite way was just bad inheritance from flattenMeshHierarchy()
it seems).
Took me a while to realize that tying this to a certain hardcoded field
isn't a good idea. The new variant is useful also for example for
getting absolute light positions or just whatever else. Besides taking a
SceneField there's now also an overload taking a field ID to avoid
double lookups. The only behavioral difference compared to the old API
is that the field is now required to exist, instead of the API being a
silent no-op if not present.
Eventually these APIs may get further extended to take a BitArrayView of
objects for which to calculate the transforms, for example to take only
meshes that are a part of the hierarchy, or meshes that satisfy an
arbitrary other condition. Which will also resolve the remaining
concerns with the API. I'm still keeping it marked as experimental tho,
the usefulness isn't set in stone yet.
The old APIs are marked as deprecated and implemented using the new
ones.
Vladimír Vondruš