Level of Detail (LOD)

[wraitii]

One issue with our graphics/rendering engine is that there is no way to use less expensive, lower-resolution models when drawing faraway objects (a system commonly known as LOD/Level of Detail).

Implementing such a system, at least for 'models' (i.e. decals, particle systems, actors) would be good; Terrain LOD is a whole other can of worms at the moment.

Key items to tick:

• model/texture/props can be activated/changed depending on drawing distance, avoiding "jittering" and "jumpiness"
• variants are preserved, so that e.g. a specific horse color is kept at various LOD
• no high CPU runtime cost to this switch, which would defeat the purpose (note that this is a memory tradeoff)

Optional but nice:

• LOD fading to avoid "popping" (see e.g. ​this)
• ...

[wraitii]

Key things that I believe should be sorted out first:

• Animations are currently per object entry when they should really be per model-def (see ​Phab:D2967)
• Getting a CModel from an ObjectEntry seems a little inefficient (may or may not be a problem)