targetting and LOS

[PaulBlay]

Originally Posted by RogerN

I think Paul's suggestion would be considerably more processor-intensive to implement. I don't see any way to get around having to track the visibility state of 16 subgrids per grid.

It's maths. But that doesn't mean that you can't fake it with tables and stuff.

[will_asher]

Take me with a grain of salt because I'm pretty sure I'm in the minority..

Why is it so important that line of sight be symmetrical?

In the following example (copied from another post), I would consider the @ to be both hiding behind the wall and peeking around it. So the @ should be able to see most of the hallway, but it should be pretty unlikely that the M would notice the @. This would involve having stealth as a factor in line of sight but I think it's much more realistic that way.

    #.#    
#####@#
..M...#
#######

The problem with assuming that the player and monsters always take the part of the grid in the middle is that any player or monster with sense is going to try to keep as much of their body as possible out of the line of fire (which should be the same as LOS).

[PowerDiver]

Originally Posted by PaulBlay

Hmm, my gut instinct was that it would be symmetrical but it doesn't appear to be the case. :-(

If the definition is asymmetrical, a point in one square and an area in the other, the result is unlikely to be symmetrical. If you want something along these lines, I think you'd have to define it as some sort of measure of the proportion of points in the two squares that can see each other. The obvious starting point for such a def would be bounds on some sort of integral, but maybe its properties would be such that there would be a simpler equivalent def once you worked out exactly what you wanted.

[Marble Dice]

Originally Posted by will_asher

Why is it so important that line of sight be symmetrical?

One good reason is that in a symmetrical visibility system, it is easy and intuitive to determine which enemies have LOS on you. If there are many asymmetrical lines of sight, then it becomes difficult to avoid situations where enemies have asymmetrical LOS on you, and it also encourages the exploitation of AI which doesn't strive to avoid being the victim of asymmetrical LOS (the classic hockey stick).

Additionally I would argue that certain asymmetrical lines of sight would make the game significantly more tactically frustrating in a bad way - consider breaking into a room with breathers in the corners with a system where the room inhabitants can see you at the door, but you can't see them. Effectively, they'd get two chances to breath on you before you could even see them, once at the door and once as you stepped into the room. The first aggressor in Angband is already at a disadvantage due to the turn-based nature of the game, and asymmetrical lines of sight only exacerbate the problem.

[Magnate]

Originally Posted by PowerDiver

However, it is exceptionally hard to get these things right and still playable, and the D&D combination of evasion and damage reduction into a single value called AC makes it impossible. The only way to fix the rule is to throw it away. That is a lesson to be considered when thinking about things like "cover" bonuses in an angband framework.

If there was one radical change I could persuade Takkaria to make to V, it would be the separation of damage absorption (armour) and damage avoidance (evasion). So much else Just Works once you sort that out.

[PaulBlay]

Originally Posted by PowerDiver

If you want something along these lines, I think you'd have to define it as some sort of measure of the proportion of points in the two squares that can see each other.

I did come up with a variation that was symmetrical, but apart from being even more complicated I had to introduce 'special case' handling to stop people being able to see the whole of rooms when in the entrance.

I won't go into details unless I can think of a relatively easy (fast running) way to implement it.

[d_m]

As far as I can tell, the biggest criticism of Eddie's original spec is that the shadows it casts aren't nice looking.

How much of a showstopper is this? After some thought, I think that attractive shadows may be incompatible with symmetry, and I definitely prefer the latter. Consider the following:

###############
#........o
#.....
#.@#
#.....
#........
###############

The orc in the picture is not visible by @ (at least, according to one of the alternate proposals). However, it seems to me that if the positions of @ and o were reversed, @ would expect to see the orc (and currently would, I think). Thus, either the system is not symmetrical, we end up with some very strange LOS situations, or it is not coherent.

EDIT: I should say that I think this argument applies to most of the systems designed to create "expanding shadows" via Eddie's argument that asymmetric beholder-beholden relationships imply asymmetric visibility.

[PaulBlay]

I think we're all getting a little confused / off track here.

To sum up, "wouldn't it be nice if"

* What you see is what you can hit with a spell (and vice versa).
* What you see can also see you (and vice versa).
* Standing directly next to a pillar should produce an expanding shadow.
* Reasonably fast code can be produced to implement the FOV, etc.
* No 'trick shots' required (or possible) to hit monsters that you can't target directly.

Is everyone agreed on the above (if they are possible)?

How does the current system specifically differ from the above?

Are any of those points not possible?

[Marble Dice]

Originally Posted by d_m

As far as I can tell, the biggest criticism of Eddie's original spec is that the shadows it casts aren't nice looking.

How much of a showstopper is this?

Considering that shadows also imply lack of visibility and thus the feasibility of cover, I think it's important. The problem isn't that they aren't nice looking so much as they don't provide adequate cover, and it's drastically inconsistent with the shadows cast on the horizontal/vertical (you're never going to fix that 100% in a square tile based system, but you can do a lot better than thin dotted line shadows).

Here's how the situation you describe would look from both perspectives, using a line from tile center to tile center for visibility, and walls obstructing from 1/4 to 3/4 inside of a tile.

Player                 Orc
#################      #################
#..............?#      #..............o#
#...........????#      #...............#
#.......@#??????#      #.......?#......#
#...........????#      #....???........#
#..............?#      #????...........#
#...............#      #??.............#
####.############      ####.############

This is a lot easier for me to believe than having a series of disconnected blind spots in a diagonal line behind a pillar. Using a line from center to center is necessarily symmetric because if you can draw a line from one direction without obstruction, you can draw the same line from the other direction without obstruction.

Paul - I agree with all your points, and I believe this system is compatible with all of them.

[PaulBlay]

Originally Posted by Marble Dice

Here's how the situation you describe would look from both perspectives, using a line from tile center to tile center for visibility, and walls obstructing from 1/4 to 3/4 inside of a tile.

Described like that you would not be able to see ghosts in the wall of corridors, nor would they be able to see you. (Because the middle of their tile is inside the wall)