How can I record movies (Doom Demos)?
First of all, cameras are just invisible players so if you want to have a camera and a real player, you must be running a server. Clients are only able to record what they're seeing. Useful commands:
recorddemo: Starts recording a demo. As arguments the command takes the file name of the demo (.CDM) and optionally the console number to record. Example: recorddemo my.cdm 2 will begin recording player number 2 into the file my.cdm. A flashing message appears telling you a demo is being recorded at console number 2.
pausedemo: Pauses the recording of a demo. Optionally takes a console number as an argument. Example: pausedemo 2 pauses the recording of player number 2.
stopdemo: Stops recording a demo. Optionally takes a console number as an argument. Example: stopdemo 2 stops the recording of player number 2.
makelocp: Create a new local player. You should be a server when using this command. A new local player will be spawned, at the specified console. For example: makelocp 1 will spawn a new local player at console 1. (Normally you always start the game as player zero.) The new player is a regular one with no special characteristics.
setcon: Change active console. Can be only used by a server. Example: setcon 2 changes the active console to player two. After giving the command the user controls player two.
makecam: Turn the given console into a camera. Example: makecam 2 turns player number two into a camera. In camera mode the view is always rendered fullscreen and HUD weapons and status bar are not drawn. Camera players are in god mode and have the noclip cheat. Moving forward means flying in the direction the camera is looking at.
setlock: Locks the view at the given player. Example: setlock 0 locks a camera's view at player zero.
lockmode: lockmode 0 allows the camera to look up and down and only locks the view horizontally. lockmode 1 is a full lock, both horizontally and vertically.
It helps to bind some of these commands to keys and/or mouse and joystick buttons for easier movie-making.
Can I convert demo movies into standard video formats?
Yes, but you'll need a video capture program, one suited to the task is FRAPs (www.fraps.com).