Should terrain be able to have vision different to movement?

[stevecotton]

Describe the desired feature

Units can already have separate vision and movement costs for a given terrain.

Terrain can already have defense calculations that are different to movement calculations, as in the many mixed terrains with

• movement = worst of (underlying terrains)
• defense = best of (underlying terrains)

However, terrains always use the movement calculation for vision too. They don't support saying "this is a rusty gate, the movement is worst of (flat, impassible) but the vision is best of (flat, impassible)", instead there are hacks such as THoT S09's trick of giving all the dwarves [vision_costs]impassable=3.

The question is, it it worth the effort to add it, will it be fun for players?

Note: there's already parts of an implementation, such as the terrain_type::vision_type() function. That doesn't get used in the pathfinding, and I'm considering removing it entirely - I just implemented a call to it from the help topic generator, only to find that it returns bogus results (saying "best of" rather than "worst of").

[CelticMinstrel]

To put it into simple and concrete terms, this seems to be a question about whether we should add vision_alias in [terrain_type]?

I'd be in favour of that, but I can't really comment on whether it would be fun.

[soliton-]

Given that there are already workarounds in mainline that this would eliminate the need for it’s definitely something to consider. I would think it generally makes more sense for vision to be best of and see no reason why we shouldn’t be able to specify that just as with movement and defense.

I think a relevant question is how much it would complicate the engine. It seems like that shouldn’t be a lot though?

[gfgtdf]

Imo different vision code than movement cose on terrain does make a lot of sense, a commom usecase is probably to make all unit be able to see over chasms.

[Jonathan-Kelly]

And see over deep water.

[stevecotton]

I've created #8818 specifically for the water and chasms. I think it would be done with [movetype][vision_costs] rather than the alias system, because it needs a way to say that something is low cost; the alias system can only say "this chasm's vision cost is best of (impassible, flat)", which still leaves merfolk with quite limited vision.