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RTG3(1)				    BRL-CAD			       RTG3(1)

NAME
       rtg3 - raytrace a model,	writing	a COVART (GIFT)	3-component format
       shotline	file

SYNOPSIS
       rtg3 [options...] model.g objects... > model.cov

DESCRIPTION
       rtg3 operates on	the indicated objects in the input model.g and
       produces	a GIFT/COVART shotline file with three components per line,
       and both	entrance and exit obliquity angles on standard output. The
       region ID field of the output file is set to the	region id of each
       intersected region (partition). If the ray partition is followed	by
       air, the	aircode	for the	air region (and	the line-of-sight thickness of
       the air)	is noted on the	shotline header	line.

       The orientation of the rays to be fired may be specified	by the -a and
       -e options, in which case the model will	be autosized, and the grid
       will be centered	on the centroid	of the model, with ray spacing chosen
       to span the entire set of objects. Alternatively, with the -M option, a
       transformation matrix may be provided on	standard input which maps
       model-space to view-space. In this case,	the grid ranges	from -1.0 <=
       X,Y <= +1.0 in view space, with the size	of the grid (number of rays
       fired) specified	with -s. This option is	most useful when rtg3 is being
       invoked from a shell script created by an mged(1) saveview command.
       Note that it conflicts with -G# and -g#;	negative hit distances have
       been seen when this conflict was	not avoided.

       The following options are recognized.

       -s#
	   Number of rays to fire in X and Y directions	(square	grid). Default
	   is 512 (512x512).

       -a#
	   Select azimuth in degrees. Used with	-e and conflicts with -M.

       -e#
	   Select elevation in degrees.	Used with -a and conflicts with	-M.

       -M
	   Read	model2view matrix from standard	input. Conflicts with -a and
	   -e.

       -g#
	   Select grid cell width. Do not use with the -s# option.

       -G#
	   Select grid cell height. If not specified, cell height equals cell
	   width. Do not use with the -s# option.

       -U #
	   sets	the Boolean variable use_air to	the given value. The default
	   for rtg3(1) is on, i.e.  -U1, but the effect	of air regions may be
	   disabled with -U0.

       -o
	   output.cov specifies	a named	file for COVART-format output. By
	   default, the	shotlines are written to stdout.

       -x#
	   Set librt debug flags to (hexadecimal) number.

       -c set ray_data_file=ray_file_name
	   specifies a file name for ray data output. This output consists of
	   one line of data for	each shotline in the shotline output file.
	   Each	line contains azimuth, elevation; x, y,	and z of the ray start
	   point; x, y,	and z of the ray direction; the	corresponding line
	   number in the shotline file;	and the	coordinates of the first hit
	   point along this ray.

       -c set rt_cline_radius=#
	   Tells rtg3(1) to use	the provided number (in	millimeters) as	the
	   additional radius to	add to CLINE solids.

       -c set save_overlaps=1
	   Tells rtg3(1) to act	like the FASTGEN4 raytracer. Specifically,
	   overlap handling is changed to agree	with that of FASTGEN4.

       The rtg3	program	is a simple front-end to librt(3) which	is most	useful
       when used with mged(1) and covart(1V).

       A color vector display of ray-model intersections can be	written	to
       rtg3.plot3 by specifying	the -X80000000 option. The resulting plot file
       can be displayed	with plot3-fb .

FORMAT
       The general layout of the output	format is:

       Overall header line (one	per run)

       View header line	(one per view)

       Ray (shotline) header line (one per ray)

       Component line (one for each three components in	this ray)

       The GIFT-3 shotline format has a	different convention for the location
       of the start point (and thus the	location of parametric distance	zero)
       along the ray. This difference is handled automatically in rtg3 by
       translating the ray's zero distance to the plane	containing the model
       origin, by adding a distance correction factor. For each	ray, both the
       cell center coordinates and the coordinates actually fired from are
       output.

       Obliquity angles	(declensions off the normal) are computed internally
       in radians but output in	degrees	to satisfy the GIFT-3 format. Note
       that internally,	librt normals always point outward, whereas GIFT
       normals point inward.

       GIFT zero-fills the fields of the component card	if there are less than
       three components. Neither COVART	II nor COVART III require this
       zero-filling, so	it is omitted by rtg3 .

EXAMPLE
       This section will acquaint the user with	the ordinary usage of rtg3 . A
       GIFT-3 output file is produced by giving	the command:

	   rtg3	-s32 model.g all.g > file

       This will make a	32 by 32 ray file of the named model. If a
       bounding-box plot file is to be made as part of producing visual
       output, use

	   rtg3	-s32 -x80000000	model.g

       The bounding boxes for the objects in the database specified will
       automatically be	put into a file	called rtrpp.plot3. Now, to compute
       the color rays use

	   rtg3	-s32 -X80000000	model.g

       The results will	be automatically stored	in rtg3.plot3. The rays	will
       be colored green	where they traverse solids in the model, and blue
       where they traverse air within the model.

       The two plot files can now be combined into a single picture and
       displayed:

	   cat rtrpp.plot3 rtg3.plot3 |	plot3-fb

OVERLAP	REPORTING
       rtg3 shares overlap handling and	reporting with the rest	of the RT
       family of applications. A brief description of the overlap reporting
       follows.

       The first one hundred (100) overlaps are	individually reported.
       Thereafter, only	one out	of each	additional one hundred overlaps	are
       reported, and the user is notified that overlap printouts are being
       omitted.	This alerts the	user that more overlaps	exist, but that	they
       are too numerous	to list	individually. The general overlap message
       takes the following form:

	   OVERLAP1: reg=region_name isol=solid_name
	   OVERLAP2: reg=region_name isol=solid_name
	   OVERLAP depth #mm at	(x, y, z) sx# sy# lvl#

       This means that OVERLAP1	and OVERLAP2 share a common space (depth) of
       #millimeters starting at	the point x, y,	z in model coordinates,	and at
       the ray coordinates (screen coordinates)	sx and sy. Level refers	to the
       level of	recursion, and will typically be zero unless glass or mirror
       objects are present.

SEE ALSO
       covart(1V), gift(1V), mged(1), rt(1), rtray(1), librt(3), plot3(5),
       ray(5V);	``COVART II - A	Simulation Program for Computation of
       Vulnerable Areas	and Repair Times - User	Manual'', Joint	Technical
       Coordinating Group for Munitions	Effectiveness, Anti-Air	Aerial Target
       Vulnerability Working Group, 61-JTCG/ME-84-3

DIAGNOSTICS
       Numerous	error conditions are possible, usually due to errors in	the
       geometry	database. Descriptive messages are printed on standard error
       (file descriptor	2).

BUGS
       The COVART file format permits multiple views to	be stored in one file.
       Rtg3 presently can only compute a single	view.

       Most deficiencies observed while	using the rtg3 program are usually
       with the	librt(3) package instead. If the -s# option is used together
       with the	-G# and	-g# options, negative hit distances will be seen.

AUTHORS
       BRL-CAD Team

COPYRIGHT
       This software is	Copyright (c) 1989-2019	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

BRL-CAD				  08/29/2020			       RTG3(1)

NAME | SYNOPSIS | DESCRIPTION | FORMAT | EXAMPLE | OVERLAP REPORTING | SEE ALSO | DIAGNOSTICS | BUGS | AUTHORS | COPYRIGHT | BUG REPORTS

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