This is the value to which the GIFTmater attribute will be set to select this material for the region.

This is the density for the material, and is specified in grams/cc.

This is a name or description the material.

#******************************************************************************
#  sample .density file for check, gqa and rtweight
#******************************************************************************
#
#     *** IMPORTANT: This file may change over time and should not be
#     *** relied upon for production analysis work.
#
#     All densities are in units of g/cm^3.
#
#******************************************************************************
#
# To use the file with rtweight, copy the file to your working directory:
#   cp GQA_SAMPLE_DENSITIES .density
#
# To use the file with check/gqa, import the file data as a binary object:
#   mged file.g bo -i u c _DENSITIES GQA_SAMPLE_DENSITIES
#
#******************************************************************************
2    7.82      Carbon Tool Steel
3    2.7       Aluminum, 6061-T6
4    2.74      Aluminum, 7079-T6
5    8.9       Copper, pure
6    19.32     Gold, pure
7    8.03      Stainless, 18Cr-8Ni
8    7.47      Stainless 27Cr
9    7.715     Steel, tool
10   7.84      Carbon Steel
12   3.00      Gunner
14   10.00     Fuel
   

Specifies which computations are to be performed and reported. The analysis_flags parameter is one or more of the following:

value	report generated
A	all
a	Adjacent different air
b	Bounding box dimensions
e	Exposed air
g	Gaps/voids
m	Weight + Centroids + Moments of Inertia
o	Overlaps
v	Volume
w	Weight

Only those reports requested will be provided. The default is -A A, to produce all reports.

Adjacent different air (a): Detects air volumes which are next to each other but have different air_code values applied to the region. This would typically indicate that the regions are different types of air, such as crew_air (which fills the crew compartment of a vehicle) and engine_air (which surrounds the engine). When these different types of air adjoin each other, it is generally considered a modeling error.

Bounding box dimensions (b): Reports the dimensions of an axis-aligned box which fully encloses the objects.

Exposed air (e): This causes checks to be made to see if the ray encounters air regions before (or after all) solid objects. It also checks to see if the ray moves from a void to an air region. Typically, only the air inside a building or vehicle is modeled if the purpose of the model is to support analysis of that single structure/vehicle. There are exceptions, such as when modeling larger environments for more extended analysis purposes.

Gaps/voids (g): This reports when there is more than overlap_tol_dist (see the -t option below) between objects on the ray path. Note that not all gaps are errors. For example, gaps between a wheel and a fender are expected (unless external air is modeled). Typically, users should perform gap analysis on contained subsets of a model (such as passenger compartments) rather than on whole vehicles.

Overlaps (o): are two regions which occupy the same space. In the real world, two objects may not occupy the same space. This check is sometimes also known as interference checking. Two objects must overlap by at least overlap_tol_dist (see the -t option below) to be considered to overlap. Overlap testing causes the grid spacing to be refined until the limit is reached, or an overlap is detected. See the -g option below for details on setting the grid spacing. Once overlaps have been detected, grid refinement is not done, and processing stops.

Volume (v): Computes the volume of the objects specified on the command line.

Weight (w): Computes the weight of the objects specified on the command line.

Not Implemented

Sets a rotation (in degrees) of the coordinate system by a given amount about the Z axis. The default is 0. See also -e .

Not Implemented

Sets a rotation (in degrees) of the coordinate system by a given elevation from the XY plane (rotation about X axis?). The default is 0. See also -a .

Enables debugging (off by default).

Specifies that density values should be taken from an external file instead of from the _DENSITIES object in the database. This option can be useful when developing the density table with a text editor, prior to importing it to the geometric database.

Specifies a limit on how far the grid can be refined and optionally the initial spacing between rays in the grids. The first value (if present) indicates the initial spacing between grid rays. The mandatory argument, grid_spacing_limit, indicates a lower bound on how fine the grid spacing may get before computation is terminated. In general, the initial_grid_spacing value should be an integer power of the grid_spacing_limit. So for example, if grid_spacing_limit has the value 1, then any initial_grid_spacing specified should be in the sequence 2, 4, 8, 16, 32... so that the grid will refine to precisely the lower limit. The grid spacing may be specified with units. For example: 5 mm or 10 in . If units are not provided, millimeters are presumed to be the units.

The default values are 50.0 mm and 0.5 mm, which is equivalent to specifying: -g 50.0mm-0.5mm or -g 50.0mm,0.5mm on the command line. This is a hard limit. If other analysis constraints are not met, the grid spacing will never be refined smaller than the minimum grid size to satisfy another constraint. The initial grid spacing is divided in half at each refinement step. As a result, if you desire a lower limit to actually be tested, then the initial grid size must be a power of 2 greater. For example, specifying -g10mm,1mm would result in grid spacings of 10, 5, 2.5, 1.25 being used. If the goal was to exactly end at a 1mm grid, then values such as 8 or 16 should have been chosen for the initial values. This would result in testing 16, 8, 4, 2, 1 grid spacing values.

Not Implemented

Specifies that the program should create new assembly combinations in the geometry database to represent the overlap pairs. This flag is meaningless if overlap reporting is not turned on with the -A option. If regions rod.r and disk.r overlap, this option will cause the creation of an assembly called _OVERLAP_rod.r_disk.r, which includes the following items:

The last item is an object to represent the overlapping area so that it can be easily seen. The default is that no groups are created.

Specifies that the grid be refined until each region has at least num_hits ray intersections. It applies only when weight or volume calculations are being performed. This limit is not applied per-view, but rather per-analysis. So, for example, it is accepted that a thin object might not be hit at all from one view, but might be hit when it is shot from other views.

The default is 1. Hence, each region must be intersected by a ray at least once during the analysis.

Specifies that only the first num_views should be computed. This is principally a debugging option.

Specifies that gqa should produce plot files for each of the analyses it performs. Depending on the analysis type(s) requested, plot files will be named with the specified prefix prepended to one of volume.plot3, gaps.plot3, overlaps.plot3, adj_air.plot3, and/or exp_air.plot3 accordingly. Plot data can be visualized in mged with the overlay command. Each of the different analysis types write to a separate plot file and use different colors for drawing.

Specifies that ncpu CPUs should be used for performing the calculation. By default, all local CPUs are utilized. This option exists primarily to reduce the number of computation threads from the machine maximum. Note that specifying more CPUs than are present on the machine does not increase the number of computation threads.

Quiets (suppresses) the "was not hit" reporting.

Indicates that gqa should print per-region statistics for weight and volume as well as the values for the objects specified on the command line.

Specifies that the grid spacing will be initially refined so that at least samples_per_axis_min will be shot along each axis of the bounding box of the model. For example, if the objects specified have a bounding box of 0 0 0 -> 4 3 2 and the grid spacing is 1.0, specifying the option -S 4 will cause the initial grid spacing to be adjusted to 0.5 so that 4 samples will be shot across the Z dimension of the bounding box. The default is to ensure 1 ray per model grid axis.

Sets the tolerance for computing overlaps. The overlap_tolerance must be a positive number equal to or greater than 0.0. Any overlap smaller than the value specified will be ignored. The default value is 0.0, which causes any overlap to be reported/processed. The value may be specified with a unit specifier such as: -t 1.0mm or -t 0.25in.

Specifies the Boolean value (0 or 1) for use_air which indicates whether regions which are marked as "air" should be retained and included in the raytrace. Unlike other BRL-CAD raytracing applications, the default is to retain air in the raytracing. The -U 0 option causes air regions to be discarded prior to raytracing. If you turn off use_air, and request any analysis that requires it (see -A above), then the program will exit with an error message.

Specify the units used when reporting values. Values must be comma delimited and provided in the order distance_units,volume_units, weight_units. For example: -u "cm,cu ft,kg" or -u ,,kg (The latter example sets only the weight units.) Note that unit values with spaces in their names such as cu ft must be contained in quotes for the shell to keep the values together.

The default units are millimeters, cubic millimeters, and grams.

Turns on verbose reporting of computation progress. This is useful for learning how the computation is progressing, and what tolerances are causing further computation to be necessary.

Specifies a volumetric tolerance value that the three view computations must be within for computation to complete. If volume calculation is selected and this option is not set, then the tolerance is set to 1/1,000 of the volume of the model bounding box. For large, complex objects (such as entire vehicles), this value might need to be set larger to achieve reasonable runtimes (or even completion). Given the approximate sampling nature of the algorithm, the three separate view computations will not usually produce identical results.

This is like the volume tolerance, -V, but is applied to the weight computation results, not the volume computation results.

The weight computation tolerance is probably more appropriate when doing whole-vehicle analysis. If weight computation is selected, it is set to a value equal to the weight of an object 1/100 the size of the model, which is made of the most dense material in the table.

gqa model.g wheel.r

gqa -g 1cm-1mm -A oe model.g hull turret suspension

gqa -g5in-0.3mm -Avw -u ft,cc,oz test.g hull turret suspension