mged — multi-display interactive combinatorial solid geometry editor


mged [-a attach] [-b ] [-c ] [-d display] [-h|? ] [-r ] [-x#] [-X#] [-v] [database.g] [mged_command]


MGED, a.k.a. the "Multi-Device Geometry Editor", is the central interaction environment for the BRL-CAD package. It offers both command line and menu driven interactions, as well as wireframe displays and integrated raytracing capabilities. It is the primary tool for BRL-CAD geometry creation and interactive manipulation.

MGED's history traces back to the earlier "GED" (a.k.a. "Geometry Editor"), and much of GED's functionality is preserved in MGED. A full description of MGED's abilities is beyond the scope of this document - the reader is referred to Volumes II and III of the BRL-CAD Tutorial Series, available at, for a more comprehensive introduction. This document will deal with the various options available when it comes to starting MGED.

The primary mode for modern MGED usage is the Tcl/Tk based environment, which offers menu support and a number of Tcl based tools. It is also possible to run more minimalist environments of terminal + framebuffer and a terminal without any display window. MGED also allows users to execute single commands from the command line without starting any environment, allowing for activities such as scripting. Some examples of such usage are present in the Examples section of this document.

Technically, MGED can be opened without a database file being supplied, but until one is supplied it will not be terribly useful. This can be done either by supplying a file name on the command line or by opening a database from within MGED using the File->Open... menu or the opendb command.

-a attach

The -a option specifies a display manager to automatically attach to when starting MGED.

Without specifying the -a attach option, MGED will prompt which display manager to attach during startup: attach (nu|X|ogl)[nu]?

The list of available display managers varies from platform to platform and across releases. However, some commonly available options are the nu (NULL) display manager, which will start MGED without any display manager attached; the X display manager, which provides an X11 graphical wireframe display; and the ogl display manager, which is similar to X but starts up a display manager that uses the OpenGL protocol for drawing wireframes.


Supplying the -b to mged will result in MGED being started as a background process. This is handy if the users still wishes to make use of the terminal from which MGED is being started.


Instructs MGED to start using classic mode instead of the default Tcl/Tk-based GUI. The -c option is often used when specifying an mged_command to indicate that MGED is being run in a command-mode without a default GUI. Example: mged -c db/moss.g tops

-d display

The -d option to MGED specifies which X server to connect to for platforms that have a running X11 server available. This option is an analogous alternative to setting the DISPLAY environment variable. You can specify a local or remote display in X11 HOST:PORT format (e.g., "-d :0" or "-d host:0") and MGED should draw windows to that display.

-h or -?

Prints out a brief help statement showing the options available when starting MGED.


Opens the database.g file in read-only mode.

-x #

Specify the debug level of librt.

-X #

Specify the debug level of libbu.


Display the version and exit.


Often it is convenient to generate a series of MGED commands outside MGED and then submit the command list to MGED, which will react as if each command were being manually entered within it. Simply create a file (say, "cmds.txt") with each line being a desired command, and then have MGED execute the list. At the normal shell prompt, execute

$ mged -c tgm.g < cmds.txt

Note that the procedure described above is very useful in rapid prototyping or automated TGM processing without resorting to low-level library programming in C or C++.


MGED database names conventionally end with .g .

SIGINT aborts the current command.

"q" or EOF exits the program.

The ".mgedrc" file is searched for in three places. The first one found is used, and any others are ignored.

  1. If the environment variable MGED_RCFILE is set, it is used as a path name for the file to be used.

  2. If the environment variable HOME is set, then HOME/.mgedrc is used.

  3. If the file ".mgedrc" exists in the current directory, it is used.


The following are run from the operating system command prompt:

Example 1. Running the MGED l from the operating system command line.

user:~ mged /usr/brlcad/share/brlcad/7.12.2/db/m35.g l component

Opened in READ ONLY mode
component:  --
   u bed
   u frame
   u cab
   u suspension
   u misc
   u power.train

Example 2. Running MGED without a display manager.

user:~ mged -c

BRL-CAD Release 7.13.0  Geometry Editor (MGED)
    Thu, 09 Oct 2008 22:31:41 -0400, Compilation 1

attach (nu|X|ogl)[nu]? nu

Example 3. Running MGED and bypassing the attach prompt by specifying the X11 display manager.

user:~ mged -a X -c

BRL-CAD Release 7.15.0  Geometry Editor (MGED)
    Tue, 22 Sep 2009 12:40:01 -0400, Compilation 1

ATTACHING X (X Window System (X11))



Computer Graphics for Target Descriptions, BRL Technical Report ARBRL-TR-02480, GED: An Interactive Solid Modeling System for Vulnerability Assessments

brlcad(1), rt(1), comgeom-g(1), vdeck(1), librt(3)


Error messages are intended to be self-explanatory.




Reports of bugs or problems should be submitted via electronic mail to <>.