This PR fixes a crash caused by the improperly ensured lifetime of RigGeometry::mSourceGeometry. mSourceGeometry was not adequate to ensure mSourceGeometry would outlive mGeometry because we extend mGeometrys lifetime beyond this lifetime by passing mGeometry to the draw traversal instead of this.
In addition,
We add important comments.
We detect and prevent generally unsafe operations in high level code.
We add a sprinkling of const to help clarify intentions.
This PR proposes a simple change to `RigGeometry` `dirtyGLObjects` logic.
1. We will avoid dirtying unmodified arrays.
2. We can drop an osg version guard since `Drawable::dirtyGLObjects` is not nearly as harmful as `Geometry::dirtyGLObjects`.
3. We will avoid crashes in an as yet unfinished future PR concerning `Array` sharing improvements.
We skip this during node path iterations. this is not a node we are interested in.
We avoid allocating a new mGeomToSkelMatrix per frame and avoid a ref_ptr associated with its update.
We speed up a search for the Skeleton node by adding a continue; condition prior to an expensive dynamic_cast.
The double buffering is an implementation detail so it should be handled as such, rather than mandating the scene graph to be structured in a certain way.
Override accept(NodeVisitor&) instead of using callbacks.
A Warning indicates a potential problem in the content file(s) that the user told OpenMW to load. E.g. this might cause an object to not display at all or as intended, however the rest of the game will run fine.
An Error, however, is more likely to be a bug with the engine itself - it means that basic assumptions have been violated and the engine might not run correctly anymore.
The above mostly applies to errors/warnings during game-play; startup issues are handled differently: when a file is completely invalid/corrupted to the point that the engine can not start, that might cause messages that are worded as Error due to the severity of the issue but are not necessarily the engine's fault.
Hopefully, being a little more consistent here will alleviate confusion among users as to when a log message should be reported and to whom.
