It's not about how to create material for decals.
It's about when/how it can be generated/placed on the surface.
E.g. is it possible to draw decals (like scratch, dirt etc) if one brush/model collide/dropdown/touch with others?
In vanilla assets I see decals only for projectiles (like bullets).
If it collide with brush then engine generate a decal, which is defined in projectile.def.
What entities (except projectiles) can generate decals? How type of collision allowed for decals?
Thanks.
P.S. On modwiki I see link to 'Alphabet Decals manual' but it sends in nowhere ((