Implement NPC culling

[JaXt0r]

Currently all NPCs are loaded immediately and shown all the time. We need to implement proper culling for performance reasons.

Investigation

• [x] Analyze the value from original G1 about the distance for culling --> ~10-15m (First mesh is made transparent, +5m, the NPC is despawned and respawned if reached)
• [ ] Implement an NPC culling manager similar to the Vob culling manager. (Maybe reuse it?)
• [ ] Handle G1 behaviour (please check with Marvin mode spawns and G1 checks for yourself):
  • [x] It seems that culled out NPCs are still "working". It means for a certain distance their invisible but still doing their routines? - yes. ~+5m distance after invisibility, they will be removed from game.
  • [x] It seems that if you're really far away, they will be completely being disabled and re-enabled when you're close by again.
• [ ] To be handled: Whenever an NPC is brought back again (e.g. Marvin mode in G1 spawning to a far away WP), the routine (e.g. for walking) is being interpolated between Routine-start and Routine-end. (You can check with the two swamp Templar walking between swamp and old mine. When you spawn next to them, they will immediately spawn at their interpolated routine route)

Implementation

• [ ] v1:
  • [x] Spawn all NPCs+Monsters when world is loaded (and do not render them until you reach their spot)
  • [x] Culling out of NPCs/Monsters after x-meters
  • [x] When spot is reached again, make the meshes visible again
  • [ ] NPCs/Monsters just restart their routines from scratch
• [ ] v2:
  • [ ] Load SaveGame and NPCs/Monsters which are inside RootObjects, will go on with their routines and spawn points based on the information stored
• [ ] v3:
  • [ ] Implement culling logic similar to G1: (1) fade out NPC/Monster, (2) destroy ~+5m further away
  • [ ] As Wld_InsertNpc() is called only once per new game start, we need to ensure, that our culling data stays the same across world switchings