obj-g - Convert a Wavefront Object (obj) file to a BRL-CAD .g database.
obj-g [-c] [-d] [-f] [-g grouping_option]
[-H plate_thickness] [-i] [-m mode]
[-o open_bot_type] [-p] [-r bot_orientation]
[-t distance_tolerance] [-u units_str] [-v...]
[-x rt_debug_flag] [-X NMG_debug_flag]
input.obj output.g
obj-g converts a Wavefront Object file to BRL-CAD's .g format.
Only face elements are supported. Materials and textures
associated with face elements are unsupported. Faces associated with
materials and/or textures will convert but material properties and textures
are ignored. Face groupings convert to BRL-CAD primitives. Any hierarchical
structure (i.e. assembly structure) defined in the obj file is not
maintained in the conversion. If a face is a member of more than one 'group'
grouping, a copy of the face will exist in each group in the resulting
model. Primitives are named based on the grouping names and have appended to
each name a string which guarantees uniqueness. This unique string includes
the obj file grouping index number, face type number (1-4), internal
conversion mode (b=native-bot|n=nmg|v=bot-via-nmg) and surface closure
status (o=open|c=closed|u=untested). Characters in the original grouping
name which may cause problems are replaced with the underscore
character.
-c
Continue processing on nmg-bomb. If this option is set
and an nmg-bomb occurs (i.e., fatal error during processing nmg or
bot-via-nmg) conversion will fall back to outputting the grouping to
'native-bot' and then continue processing the next grouping. If this option is
not set and an nmg-bomb occurs then all processing will stop and the converter
will exit.
-d
Output debug information to standard error. Because
-d results in an extremely large amount of information, it is strongly
suggested that standard error be redirected to a file.
-f
Fuse vertices that are within distance_tolerance
of each other. This can make the solidity detection more reliable, but may
significantly increase processing time during conversion.
-g grouping_option
Choose which face grouping, as defined in the obj file,
to use to create the BRL-CAD primitives. The grouping_option may be one of
(g|o|m|t|n) where g = group (default), o = object, m = material, t = texture,
n = none. Choose a grouping option which will produce the appropriate
primitives for the intended use of the resulting model. Typically not all
groupings exist in every obj file. Do not choose 'none' as the grouping option
unless you have a specific need for no grouping. Choosing 'none' for a large
conversion will significantly increase the time and system memory required for
a conversion to complete. Choosing a grouping which does not exist in the obj
file has the same effect as choosing 'none'. Note: It is possible for a single
grouping to produce up to four primitives due to the four possible face types
that can exist in an obj file. The values of the index numbers appended to the
end of the primitive names will give an indication if this has occurred.
-H plate_thickness
Plate thickness in mm units of plate or plate-nocos bots
created when the bot is not a closed volume. This option is ignored unless the
open_bot_type is set to 'plate' or 'plate nocos' (see -o option).
-i
Ignore normals defined in the obj file when the
conversion mode is 'native-bots'. This option has no effect when the
conversion mode is set to 'nmg' or 'bot-via-nmg', where provided normals are
always ignored (see -m option).
-m mode_option
Choose the conversion mode. The mode_option may be one of
(b|n|v) where b = native-bot (default), n = nmg, v = bot-via-nmg. The
'native-bot' mode is best for a relatively quick conversion where creating
solids is not the highest priority. It attempts to identify surface closure
(solids) but is not as robust as 'bot-via-nmg'. It is the only mode that
supports use of the obj file normals. The 'bot-via-nmg' mode is the best
option for creating solids (i.e. volume-mode-bots).
-o open_bot_type
Type of bot to create when the primitive is not a closed
volume. open_bot_type can be (s|p|n) where s = surface bot (default), p =
plate bot, n = plate-nocos bot. Generally use 'surface bot' if open surface
thickness is irrelevant or the purpose of the resulting model is strictly
visualization. Use 'plate bot' or 'plate-nocos bot' when open surfaces must
have a defined thickness. Note: An incorrect plate thickness can create
geometry overlaps. Use the '-H' option to define plate thickness.
-p
Plot open edges when creating bots which are not a closed
volume. A plot/overlay (.plot3) file will be created with the same name as the
bot primitive and be placed in the current directory. If a plot file already
exists, it will be overwritten. Closed edges are closed but open edges are not
necessarily open. This is due to limitations of the algorithm for identifying
open edges.
-r bot_orientation
Orientation type to use for bot primitives.
bot_orientation can be (1|2|3), where 1 = unoriented, 2 = ccw, and 3 = cw; 1
is default.
-t distance_tolerance
Maximum distance, in mm units, where two vertices are
considered the same. The default is 0.0005mm, which matches the default
raytracer distance tolerance. Do not change this value unless you also change
the raytracer distance tolerance.
-u units_str
Units of obj file, where units_str can be any valid
BRL-CAD unit such as (m|cm|mm|ft|in) or a custom conversion factor from obj
file units to mm.
-v
Output verbose user information to standard error
(stderr) stream. There are different levels of verbose output where higher
levels increase the amount of output information. Each occurrence of this
option in the parameter list increases the verbosity level (two levels
currently). A large amount of information will be output so redirecting stderr
to a file is highly recommended. Verbose messages add warning and detailed
conversion status messages to the default status and error messages. -v
must be enabled for warning messages to be reported.
-x rt_debug_flag
Specifies debug bits (see raytrace.h).
-X NMG_debug_flag
Specifies debug bits for NMG's (see nmg.h).
input.obj
The path and file name of the input WaveFront Object
file.
output.g
The path and file name of the output BRL-CAD database
file. If this file already exists, it will be overwritten.
The following will convert the obj file input.obj to the BRL-CAD database
output.g.
Example 1. BOT Conversion
obj-g -u mm -i input.obj output.g
Convert obj file 'input.obj' to BRL-CAD database file 'output.g'
using native-bot conversion mode. Non-closed surfaces will be output as
surface-mode bots; closed surfaces will be output as volume-mode bots.
BRL-CAD primitives will be created based on the obj file 'group' grouping.
The obj file units are set to millimeters (implies conversion factor of
1.0). Any normals specified in the obj file are ignored. All messages will
be sent to the display.
Example 2. BOT via NMG Conversion
obj-g -m v -o p -H 5 -g o -v -v input.obj output.g 2>
output.log
Convert obj file 'input.obj' to BRL-CAD database file 'output.g'
using bot-via-nmg conversion mode. Non-closed surfaces will be output as
plate-mode bots, with plate thickness of 5mm. Closed surfaces will be output
as volume-mode bots. BRL-CAD primitives will be created based on the obj
file 'object' grouping. The obj file units are assumed to be meters (implies
conversion factor of 1000.0). Level two verbose messages are enabled. All
standard-error messages are sent to the log file 'output.log'.
Numerous warning and error conditions are possible, usually due to invalid
source geometry. Descriptive messages are printed on standard error (file
descriptor 2). -v must be enabled for warning messages to be printed.
This software is Copyright (c) 2010-2019 United States Government as represented
by the U.S. Army Research Laboratory.
Reports of bugs or problems should be submitted via electronic mail to
devs@brlcad.org
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