The 3DGE console is a text-only command-line interface that tracks game and system messages and allows the user to enter commands (CCMDs) and edit variables (CVARs).
Using the Console
The 3DGE console can be accessed by pressing the tilde key (~) by default. When pressed, the console will appear from the top of the screen and extend downwards to fill half the screen during gameplay. However, unlike other ports, the game will not pause when the console is called. Commands can be typed directly at the prompt in the console, allowing the user to modify a variety of game settings, activate cheats or debugging features, and otherwise take direct control over the game engine.
When using the console, there are a few hotkeys that have a special function. You can scroll the console forward and back using the Page Up/Page Down keys, or by scrolling the mouse wheel. When the console is scrolled up, the prompt will remain visible, but there will be a row of uppercase V's above it indicating that some of the console log has been hidden.
Pressing the up and down arrow keys will cycle through a list of recently-typed commands.
You can close the console and return to the game by pressing the tilde key (~) while the console is open.
Console variables, or CVARs, are variables that may be changed by the user that control everything from the game type to the number of decals to display on the walls. They are typically divided into a number of categories and identified based on their prefix. For example, r_fadepower is part of the Video category, while debug_joyaxis is part of the of the Debug category of variables. Not all CVARs will fit this mold, however.
You can find a list of variables supported by 3DGE, along with their descriptions here. You can also get a list in the console by using the cvarlist console command.
Console commands are commands that can be executed from the console. Unlike CVARs, they are not categorized by name. However, for the purposes of documentation, the wiki does divide them into several categories based on their area of use.
You can find a list of commands supported by 3DGE, along with their descriptions here. You can also get a list in the console by using the showcmds console command.