TECHNICAL NOTES FOR TREDSOFT.WAD

    Okay, okay. Some of you may have figured out how the landmines in
TREDSOFT work, but don't know exactly why or what the limitations are.
Others may simply have no clue.
    That's what this file is for. Essentially, the concept is a very
simple one--it's just rather obscure and technical. It deals with
player starting positions, and teleportation.

    A very curious feature of the Doom engine is that, while multiple
Deathmatch starting positions result in a random start point, multiple
single-player starts do not. When you place more than one Player One
starting point in a level, the starting point is not randomized--what
happens is that a "ghost" player--a simulacrum, if you will--is
created at every startpos other than yours. The place where you
actually come in is the startpos (which is a "thing" in the DEU
interface) with the highest Thing #.
    These simulacrums have special properties. They do not affect
sector types (acid floors do not hurt them, and they do not trigger
secret sectors). They do not move, although they can be moved by
gunshots and blasts. Monsters will not attack them directly, although
they can be caught in the line of fire. They are affected by area
effects, projectiles, gunshots, and they can be crushed by ceilings.
They have 100% health to begin with, but no armor. In effect, they
stand still and are ignored. However--and this is the key--any damage
which is done to them, happens to you. If they take damage, you take
it as well. If they are killed, you die as well--regardless of your
own health status.
    This is where the teleporter comes in. If you look at Tread
Softly! in DEU, you will see many small hexagon-shaped sectors
littered around the level. The linedefs of these sectors are defined
as W1-Teleport, and are all flagged to go to the same sector. Inside
this sector is the required teleport exit, and in *exactly* the same
spot is a duplicate Player One startpos, which I placed first to
ensure that the player entered the game in the other one. These small
sectors simulate "landmines" by strobing their light levels as a
subtle warning of their presence, and when you "step on" one by
crossing the teleport linedef, you are teleported to the other sector,
thereby *telefragging* yourself.
    For those of you who don't know what telefragging is: In the Doom
engine, no two objects may occupy the same X,Y coordinate at the same
time. When two killable objects (such as a player or a monster) teleport
into the same spot, the thing which was there first is fragged.
Mushed. Toast.

    There are numerous possibilities for the multiple-player startpos
feature. I will leave it up to your imagination, and close this by
listing the only real limitation I've found thus far, and that is
that this feature works *only* for single-player levels--it will not
work on cooperative or deathmatch mode, sorry. :) I wish, eh?

    Brandon Bannerman
    backtrak@shadowplay.com
    May 1995