OBJ-G(1)

NAME

obj-g - convert a Wavefront OBJ file to a BRL-CAD database

On this page

SYNOPSIS
DESCRIPTION
OPTIONS
EXAMPLES
SEE ALSO
AUTHOR
COPYRIGHT
BUG REPORTS

SYNOPSIS

obj-g [-cdfipv] [-g _grouping_] [-m _mode_] [-o _open_bot_type_] [-r _orientation_] [-H _plate_thickness_] [-t _distance_tolerance_] [-u _units_] [-x _rt_flag_] [-X _nmg_flag_] _input.obj_ _output.g_

obj-g converts the polygonal face elements of a Wavefront OBJ file into BRL-CAD bot(5) primitives stored in a .g database. Materials and textures are parsed but ignored; only geometry is converted. Each OBJ face grouping becomes a separate primitive, with no assembly hierarchy preserved. If a face belongs to more than one group, a copy is created in each. Primitive names derive from the OBJ grouping names, with characters that are invalid in BRL-CAD names (such as '/', '\\' and '=') replaced with underscores.

By default conversion uses native-bot mode, grouping by OBJ group ('g') elements, with OBJ units assumed to be meters.

OPTIONS

-c: Continue processing after an NMG bomb. On a fatal error in nmg or bot-via-nmg mode, fall back to native-bot output for that grouping and proceed; otherwise the converter stops.
-d: Output debug information to standard error. This produces a very large amount of output, so redirecting standard error to a file is recommended.
-f: Fuse vertices that fall within the distance tolerance of one another. Improves solidity detection but can significantly increase conversion time.
-g grouping: Select which OBJ face grouping is used to create primitives: g = group (default), o = object, m = material, t = texture, n = none. Selecting a grouping absent from the file behaves like n; n greatly increases time and memory for large models.
-H plate_thickness: Plate thickness in mm for plate and plate-nocos bots created from open (non-closed) volumes. Ignored unless -o p or -o n is in effect.
-i: Ignore the normals defined in the OBJ file when using native-bot mode. Has no effect in nmg or bot-via-nmg mode, where provided normals are always ignored.
-m mode: Select the conversion mode: b = native bot (default), n = nmg, v = bot via nmg. Native-bot is fastest and is the only mode that uses OBJ normals; bot-via-nmg is best for producing solid (volume) bots.
-o open_bot_type: Type of bot created when a primitive is not a closed volume: s = surface (default), p = plate, n = plate-nocos. Use a plate type (with -H) when open surfaces need a defined thickness.
-p: Create a plot/overlay (.plot3) file of open edges for each bot that is not a closed volume. The file is named after the bot primitive, written to the current directory, and overwrites any existing file.
-r orientation: Bot orientation: 1 = unoriented (default), 2 = counter-clockwise, 3 = clockwise.
-t distance_tolerance: Maximum distance in mm at which two vertices are considered the same; default 0.0005. Should match the raytracer distance tolerance, so do not change one without the other.
-u units: Units of the OBJ file: a BRL-CAD unit name such as m, cm, mm, ft or in, or a custom numeric conversion factor from file units to mm. Default is m.
-v: Output verbose information to standard error. Repeat to raise the verbosity level (two levels currently). Warning messages are only printed when -v is given.
-x rt_flag: Set librt debug flag bits (see raytrace.h).
-X nmg_flag: Set NMG debug flag bits (see nmg.h).

EXAMPLES

Example 1. Quick native-bot conversion in millimeters

obj-g -u mm -i model.obj model.g

Converts model.obj using native-bot mode with a unit scale of 1.0 (OBJ units are millimeters), ignoring any normals in the file. Closed surfaces become volume bots and open surfaces become surface bots, grouped by OBJ 'group' elements.

Example 2. Watertight solids via NMG, logging to a file

obj-g -m v -o p -H 5 -g o -v -v model.obj model.g 2> model.log
mged model.g 'tops'

Converts model.obj with bot-via-nmg mode for robust solid detection, emitting 5mm plate bots for open volumes and grouping by OBJ 'object' elements (file assumed to be in meters). Level-two verbose output is captured in model.log, then mged(1) lists the resulting top-level objects.