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IDENTS(5)

NAME

idents - BRL-CAD idents file format

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FORMAT

An idents file is a line-based plain text file containing identifiers, properties, and path information for BRL-CAD geometry. Typically generated by the idents command in mged or archer, the idents file contains information for a list of regions. The identifier data written for each region includes a sequential region count, a region identifier (a.k.a. the "ident" number), an air code, a material code, a line-of-sight (a.k.a. "LOS") thickness factor, and the path to the region.

Each line constitutes a record. Lines with non-whitespace in the first character position of the line (i.e., character position 0) are considered comments. By default, there is both a header and a footer with additional information including the file name, title, units, objects, and details on the file’s original creation.

Lines beginning with a space (i.e., character position 0) are considered region records with six columns separated by whitespace. As region paths may contain spaces, the last column continues until an end-of-line colon (:) character. The columns are described in following:

column 1: region Count

For output purposes only, each region is assigned a number based as it’s encountered in the output hierarchy.

column 2: region ID

Region identifiers for solid geometry are non-zero numbers representing a single homogeneous material object (i.e., a part). This value is encoded as the "region_id" attribute on region objects.

Region IDs need not be unique, but may be reassigned uniquely using the reid command in MGED.

Negative region IDs canonically indicate an air region.

column 3: air code ID

All regions representing "air" can have an identifier number set on them, encoded as a positive-valued "aircode" attribute on region objects. Regions marked as air are typically handled differently by applications (e.g., the rt utility ignores them by default during rendering unless the -U option is specified). Air regions also can exhibit different overlap behavior.

column 4: material ID

All regions can have a material identifier set on them, encoded as a non-negative "material_id" number. All objects consisting of the same material typically are encoded with the same material ID value. What the value represents is encoded in a separate file, table, or object and can be extracted using various commands (e.g., see the material and mater commands in MGED).

column 5: line-of-sight thickness factor

All regions can have a light-of-sight thickness factor (a.k.a. "los") set to indicate its proportional representation of material homogeneity. That is, it indicates what percentage of a given object is the material specified.

Line-of-sight factors are typically used in place of modeling detail. For example, one might model a radio that in reality has circuitry, wires, air voids, and more as a simple box with material_id set to a code representing aluminum and los set to 10. This would indicate, for analytic purposes, that the box is 10% aluminum by volume.

column 6: geometry path

The last column contains the full path to a given region. As paths may contain spaces and other characters, the path and lines are terminated with a colon (:) character.

EXAMPLES

1 -8    Summary Table {idents}  (written: Wed May 11 14:37:52 2022)
2 -7         file name    : /path/to/db/moss.g
3 -6
4 -5
5 -4         user         : Christopher Sean Morrison
6 -3         target title : Gary Moss's "World on a Platter"
7 -2         target units : mm
8 -1         objects      : all.g

 1    1000    0    0    0  /all.g/platform.r:
 2    2000    0    0    0  /all.g/box.r:
 3    3000    0    0    0  /all.g/cone.r:
 4    4000    0    0    0  /all.g/ellipse.r:
 5    6000    0    0    0  /all.g/tor.r:
 6    1000    0    1  100  /all.g/light.r:
* 9999999
* 9999999
* 9999999
* 9999999
* 9999999

UTILITIES

mged and archer have several commands which set identifiers and read/write idents files.

SEE ALSO

idents(n), reid(n), remat(n), reg_def(n), material(n), mater(n), edcodes(n), rcodes(n), wcodes(n), mged(1), and archer(1).

AUTHOR

BRL-CAD Team

This software is Copyright (c) 1989-2026 by the United States Government as represented by U.S. Army Research Laboratory.

BUG REPORTS

Reports of bugs or problems should be submitted via electronic mail to devs@brlcad.org