To create a DMO file start the game with the command line switch
/r (and /l (level), /s (skill) etc.) and play as
usual. If you press F10 the record (and the game) stops.
You will find a file demo1.dmo in the current directory. To play it
back just start the game and hide the menu by pressing ESC.
In Duke Nukem 3D 1.0 and 1.1 the skill value is a bit strange:
To record a skill n (1<=n<=4) game note to use
/sn+1.
So /s2 is ``Peace of Cake'' and /s5 is
``Damn I'm Good''. The dn3dhelp.exe hint
(/sn with 0<=n<=3) is totally wrong.
Multiplayer recordings have always the skill 0. Cooperative recordings won't play back properly.
It is impossible to record with version 1.0 more than one level. You can't even record the summary screen at the end of each level.
In version 1.1 it seems to be possible (I got it some times). Some other times I got only the recording of the last level.
A DMO file records all player actions. The monster movements, respawn positions etc. are totally deterministic. The messages during a multiplayer game (macros and RemoteRedicule (tm)) do not appear in the DMO.
A DMO file consists of a header with some organizational information and the data area with all the (compressed) game tics.
The term ``game tic'' comes originally from DOOM and denotes the smallest unit of time during the game. The duration of a game tic is 1/30s. To store a game tic in a file means to store all actions, like movement, open doors, fire weapons and so on, happened during this time.