To avoid triggering NavMesh update when RecastMesh change should not change
NavMesh.
Based on the following assumption:
Given a set of transformations and a bounding shape for all these
tranformations, a new object transformation that does not change this
bounding shape also should not change navmesh if for all of this object
transformations resulting navmesh tiles are equivalent
The idea is to report back to RecastMeshManager all changes of NavMesh if there
are any assiciated with RecastMesh version. So we know the last time when
RecastMesh change resulted into the NavMesh change. When later report shows
that there was no NavMesh change for a new RecastMesh version we can assume
that any object transformation within the same bounding box should not change
NavMesh.
mLastBuildRevision == mRevision with current use cases does not happen. But
even if this will happen when another use case will be added it does not save
much computation. The most expensive operation is not adding objects to the
MeshBuilder but to optimize resulting navmesh that will happen anyway in
MeshBuilder::create call.
Use LRU modification to hold currently used items. Use RecastMesh binary
data for item key.
Store original pointer of btCollisionShape in user pointer to make available
it as an identifier within all duplicates. Use pointer to heights data array
for btHeightfieldTerrainShape.
