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== Third dimension in an ASCII-based roguelike ==

by [[Kornel Kisielewicz]]

Sounds crazy, eh? Well our world is apparently three dimensional. So why
should a roguelike map be only 2D? Of course this article considers only the
serious reality-based roguelike games - Crawl is 2D and it is fine.

So what do I mean "ASCII-3D-roguelike"? No, I don't want to add 3D-models 
and do a QuakeTT style game. What I'm thinking about is a 3D map, that 
also has a "z" component. Why the hell, you might think?

== Advantages ==

# the possibility of realy flying enemies (you can be overflown) without hack's.
# a truly 3D system of dungeons, where you can fall from a gallery, or climb up a ladder, or swim underwater... possibilities are endless.
# underwater action - cities, caves
# Thief-style game, where you sneak on top of the town's roofs, trying to sneak past the townguards. Moreover, a assassin on the roof... at last jumping and climbing comes in handy.
# a real ability to fly
# complicated interconnected Castle buildings, where you can actually walk around the roofs. A lot inspiration for political/assassin games.
# a truly mountainous landscape, hiding behind hills, charging downhill
# patrolling the city walls at night, trying to sight an enemy
# a real siege scenario
# and more...

Ok, so 3D is a NiceThing(tm). So why don't we plug it in?

== Problems and Solutions ==

# a extended map object (space consumption, more coordinates)
# monster AI that takes into account the third dimension
# a new raytracer or light engine for three dimensions
# a way to represent elevation on the map
# and more...

Point number 1 is quite easy -- space isn't so much restricted (if you do
level compression), the additional coordinate can be implemented easy (if
you're doing it from the beginning, that is). Calculating distance may be
done easy with the formula:

   3D Distance = Max(D,H) + Min(D,H)/2
     D = 2D Distance (x,y)
     H = Difference in height

Point 2 would still be possible, although you would have to remember to alter
the spotting chance depending on the difference in elevation. Flying
creatures are a little more tricky though. It is wise to change the cost of
moving up and moving down for flying creatures and for walking ones as well
(it's easier to run downhill then uphill).

It's point number 3 will cause trouble, light has to be treated as a sphere
and not a circle, and standing on the middle of a roof, you wont see what is
just by the building's wall.

But the real killer is point 4. It still isn't a problem if you use graphics
or more than 16 colors. But if you're trying to mage a hardcore 16 color
ASCII-based game -- then you're in trouble.

A way to do it is just to show the current elevation -- but then many
possibilities are closed (you can't see from a roof where the guards on the
bottom are). So we need some kind of representation for the lower levels (we
ougth to have a representation for higher levels, but as far as I can think
of it, it's pure science-fiction...). Another idea, taken from the UFO game
is to have a key, to cycle through the levels -- seems good, but it's quite
inconvienient to do that every time when you wan't to see what's happening
below.

Of course you can treat higher elevation as seperate levels, but that
seriously impairs on their interaction capabilities.

IMHO the best way to resolve this problem is to make all the sqares below the
player DarkGray... but then, how will we see the light on them? I need more
shades of Gray! There is a problem still with creatures flying high --
maybe a shadow on the ground (that is a gray tile?).

On the other hand, this could be a very good use case for 2.5D display system
such as goggles that simulate 3D objects or even upcoming 3D display systems
that no longer have a need for goggles.
("I, for one, welcome our 2.5D roguelikes" ;) )

== Things to remember about ==

# gravity -- items dropped in air will fall, so will corpses of killed flying creatures. So will the player if his "Fly" spell ends...
# targeting -- here keys like PgUp PgDown for switching between levels would come in handy.
# hurling grenades over walls -- just think about it...
# explosions (e.g.fireball) -- do they affect creatures over you?
# jumping -- how to implement it?
# roofs -- there is a difference wether a tile is just empty, or non-existent -- that is a floor on level two seperates the levels, an air tile doesn't
# and more...

== 3D Roguelikes ==
*[[CastlevaniaRL]] and [[MetroidRL]] http://www.santiagoz.com/web
*[[Wish]], available at the [http://www.graveyard.uni.cc/ Roguelike Graveyard].

[[Category:Articles|Third dimension in an ASCII-based roguelike]]