ToME: the Tales of Maj'Eyal

I did a little effort to visualize what it could look like if we added front and back to actors (including the player) and gave them conical FoV.

* Adding front and back would allow to give combat bonus when attacking from behind or from the side of a creature (seems like a nice bonus to for example rogues). This encourages tactical play: Daze and move behind the target to deal more damage, or use pinning attacks and movement infusions to position yourself and attack from the side or from behind. To attack you, the npc has to move first to turn around (turning around could be a fast move action, and would happen when you bump into something that is not in your FoV).
* It would allow for avoiding detection by staying behind the NPC's commando's style (for those that do not know the commandos series, check this video: http://www.youtube.com/watch?v=lY8d-OPByWU). The makers of commandos basically made an entire game around the idea of sneaking around FoV.
* You can only shoot/target things in your FoV so your direction becomes important.

To 'see' the FoV the player could press a hotkey, showing the field of view of all actors on the screen.

Some additional ideas:
* You look in the direction you move, so running away exposes your back.
* You can walk backwards, but slower, by holding modifier_key+movement.
* There could be a 'look over your shoulder command' that allows you to look in any direction (swift action - only one each turn and no action cost - or just a fast action)

Here are the pictures of what could be considered attacking from front, side or back, and what FoV might look like on the diagonal and on straight lines.

This would be pretty spiffy and certainly open up more realities to combat in a variety of ways. Facing tends to be rather important in many P&P schemes as well, so implicit support for it would be yet another strong feather in T-Engine 4's cap to hopefully tempt some more computer game adaptations into being.

I think this would be very interesting, and could allow us to further diversify monsters/create new abilitiesthat alter your field of sight.

A horror might be able to see all around itself, and really have no front or back, while a helmet or special ability(Necromancer? Corruptor?) could literally give the player eyes on the back of their head.

However..., it would likely be a huge change and possibly require significant AI tweaking, too. So not really likely to happen I think.

I don't really like facing in roguelikes. It's difficult to implement, tedious to play, and nigh-impossible to indicate on NPCs without piles of display options.

I am 100% against this idea. Facing has never been done well in roguelikes. As bricks says it is tedious as hell. You end up needing separate commands to turn and just moving about becomes an enormous chore. Normal dungeon exploring takes twice as long, and quite frankly the supposed added tactical depth is normally just dull. Also a game that involves this has to be built from the ground up on the basis - it can't be something simply tacked on.

That said, the engine does already support this, for anyone who wants to make a module with such a feature.

I agree that I dislike the facings because I'd lose so much tactical information, but if you want to add it in a module, by all means go ahead.

Just out of curiosity, can anyone point out a rogue-like that has a similar feature as discussed here?

Gearhead does. However, Gearhead is designed primarily for short combat 'scenes' where every move you enter can be a matter of life and death -- it's not really a dungeon crawler, so it works a lot better there.

Gearhead does a lot of things that make it less painful. Most important by far is that facing does not affect your FoV, only your targeting arc and active defenses (parries, etc.) This in turn allows you to use 'normal' roguelike movement whenever you're not in combat without having to worry about facing at all (the game automatically turns you to face whatever direction you hit, taking the necessary time -- likewise, if you try to target someone outside your targeting arc, the game simply has you turn automatically, so you don't need to worry about facing against weaker opponents where the time spent turning is not a big deal.)

So targeting arcs can work. In general, though, implementing FoV in a roguelike sucks, since it makes it flat-out painful to do basic things like exploring. And the AI isn't good enough to use it, either (remember, right now it doesn't even use light radius! All AI actors get Infravision for free.)

Also, gearhead is meant to be 'mechanical' in feel -- by default, it uses roguelike controls for 'personal-scale' actions (which are most of what you do when you're not fighting) and detailed directional controls for mecha combat. Since controlling that in detail feels like driving a tank, it works for a game like that...

It wouldn't work for playing an elven wizard, I think.