Implement quality levels for actors & corresponding setting.
An actor file, as referenced by the VisualActor, can now define different actors for different "quality level" setting.
In this initial version, the quality is handled directly by the object manager.
Actor format impact:
- '<qualitylevels>' may be used as the root node, containing actor nodes as children.
- such actor nodes can refer to a file, or to an inline actor, or simply be inlined.
- such actor nodes may have a 'quality' attribute, specifying the maximum quality level of this actor. By default, 255 (the maximum) is implied.
- The actor format remains valid, but 'groups', 'variants', 'material', 'castshadow' and 'float' can be given a [minquality, maxquality[ range via XML attributes. Outside of this range, the XML node is ignored (making it possible to define, in a single actor file, several quality levels).
Quality is a 0-255 value, with:
- Range 0-99 intended for lower level-of-detail actors (billboards, etc.)
- Range 100-200 the 'normal' range for models. 100 is "low", 150 "medium", and 200 "high".
- Range 201-255 used for higher quality actors that might be used for e.g. cinematics.
The range is wide to make it easier to add intermediate levels in the future and it seemed easier given that an integer value of some kind was required anyways.
- A new CActorDef class is introduced, wrapping an art/actors XML file and its different quality levels. ObjectBase remains the definition of a given 'actor', now at a given quality level.
- CActorDef imposes a maximal # of quality level for a particular actor definition (5 currently).
- CUnit is made to refer to an Actor Definition explicitly, not a particular ObjectBase.
- As a minor optimisation, variation keys are calculated on pointer-to-sets-of-selections, instead of raw sets-of-selections, as this reduces copying.
- some refactoring, including better const-correctness and hotloading support via std::shared_ptr.
Differential Revision: https://code.wildfiregames.com/D3787