g-shell-rect — Produce triangulated shell from BRL-CAD model


g-shell-rect [-a rpp_args] [-R edge_tol] [-p plotfile] [-X lvl] [-d debug_level] [-b ] [-n ] [-i initial_ray_dir] [-g cell_size] -o brlcad_output_file database.g object(s)


g-shell-rect converts the specified objects(s) from a BRL-CAD model database.g to a single NMG solid using raytracing. Rays are fired in a uniform grid. The direction for the first set of rays is chosen by calculating the presented area of the bounding box of the object(s) and selecting the direction with the largest area. The user may override this by specifying a desired initial ray direction using the -i option (see below). The initial shell is constructed using only the first and last intersections with the object(s). This will typically result in some rather large faces with normals at right angles to the ray direction. Unless the -n option is specified, these faces are then subdivided (according to the cell_size) and additional rays fired from the other two directions are used to refine their shape. The resulting NMG solid will be named shell and will be written to the specified brlcad_output_file.

The following command line options are recognized:

-g cell_size

Specify the dimensions (in millimeters) of the grid spacing. The default is 50mm.

-i initial_ray_dir

Specify the initial ray direction. Valid values are X, Y, or Z. The best results are usually obtained by raytracing in the direction that produces the most hits first.

-d debug_level

Set the debugging level. Higher values produce more debugging information.


Suppresses the refinement stage (firing rays from the secondary and tertiary axis directions).


Output a BOT rather than an NMG.

-a rpp_args

Add an RPP for refining.

-R edge_tol

Supply edge tolerance.

-p plotfile

Supply plotfile for plot edge breaking.

-X lvl

Supply NMG debug flags.

-o output.g

Specifies the name of the BRL-CAD geometry file to create.


$ g-shell-rect -o shell.g sample.g sample_object


Error messages are intended to be self-explanatory.




This software is Copyright (c) 1998-2016 by the United States Government as represented by U.S. Army Research Laboratory.


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