The previous lazy rendering means the snapshot of the render state might be more up to date then when the frozen actor actually did become visible. Now, we take this snapshot as soon as needed. We still retain the performance of only doing this rendering when needed by avoiding extra rendering until the visibility cycles again.
Deferencing an array element to get the state is cheaper than a dictionary lookup. We can do this since the players collection does not change during gameplay.
Provide some common extension methods to reduce code duplication, and also use loops instead of LINQ to reduce allocations and provide a minor speedup.
Previously actors that could be frozen under fog but were currently visible would be rendered by the frozen under fog system constantly in order to keep a copy of the renderables ready to go for the frozen counterpart when the actor became invisible. Instead, we now delay this extra rendering until the actor actually becomes invisible. This eliminates the wasted rendering to generate renderables that were never used.
The FrozenUnderFog.Tick method will now reuse the calculation do by the frozen actor when it had to calculate its visibility, this prevents it having to re-do the fairly expensive visibility calculation.
To resolve the ambiguity introduced when the introduction of isometric maps meant that cell and map coordinates were no longer equivalent, a new type has been introduced so they can each be represented separately.
