What is exactly the funcion of the unit_sprites lines in the battle_models.modeldb file?

[FJMS1988]

Hello everybody, I am writing here because I have a little question and I would be very happy if someone could help me. My question is; what is exactly the function of the unit_sprites lines in the battle_models.modeldb file? I have been modifying this file and I have been creating some new units so I know the meaning of the information this file has, the only thing I don’t know what is for are the unit_sprites lines like this one:

49 unit_sprites/england_Dummy_EN_Spearmen_sprite.spr

Thank you very much in advance.

[Taiji]

When you zoom out far enough, the engine replaces the 3d models with 2d sprites.

If you're making new units then the simplest approach to using sprites, is to use an existing one which is approximately the same colour as your new units.

The only important thing to note about them, and that many mods (like SS and DLV) messed up on, is that you cannot use a mounted unit's sprite for infantry. Doing so results in infantry that have no legs at the sprite viewing range.