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Man Pages

Manual Reference Pages  -  SECPASS (1)

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secpass - interrogates an mged file to obtain the conductivity table of the PRISM-ready input file or a generic thermal data file



secpass model.g objects...


Secpass is an interactive program used to create a conductivity table for the PRISM-ready input file (when used in conjunction with firpass) or a generic thermal data file. The conduction approximation is based on the following formula from the PRISM manual.

        RK(i,j) =             1
                      L(i)/K(i)A + L(j)/K(j)A

        RK(i,j) - conductivity between region i and j         L(i) - conduction path length of region i         L(j) - conduction path length of region j         K(i) - conductivity of material of region i         K(j) - conductivity of material of region j         A - shared surface area

The conduction path length is a distance between the centroid of the region and the shared surface. The user may select the average, root mean squared (rms), minimum, or maximum distance for the length.

The following information about each region is obtained from secpass when creating a PRISM ready file.

        number (same scheme as in firpass)
        number of region there is conduction between

The following information about each region is obtained when creating a generic thermal data file

        number of adjacent regions
        shared area of each adjacent region (m**2)
        conduction distance (m)


The following is an example from an interactive session.

$ secpass test.veh.g vehicle air
Write output to standard out (0) or a file(1) not at all (2)?  2
Enter name of file that has second pass information
in it (15 char max).  veh.f.2nd
Enter type of output file to be generated.
         0 - PRISM File
         1 - Generic File
Enter name of file to be created for PRISM conductivity
information (15 char max).  veh.s.con
Which release of PRISM is being used, 2.0 (2) or 3.0 (3)?  3
Which length calculation should be used when
computing conduction
between regions?
        1 - average length
        2 - rms length
        3 - minimum length
        4 - maximum length
Enter name of file to be created for conductivity
table (15 char max).  veh.s.tbl
Enter name of material file (15 char max).  prp
Enter name of error file to be created (15 char max).  veh.s.err
Should there be 3 sets of orthogonal rays fired (0) or 1 set (1)?
3 sets of orthogonal rays will be fired.
Database title:  test vehicle for use with irprep programs
Number of regions in mged file:  21
Mallocing arrays.
cond malloced
loop malloced
All variables zeroed.
second pass file opened
The number of regions read was 21
Center of bounding rpp ( 356.500000, 0.000000, 1250.000000 )
Length of diagonal of bounding rpp:  3829.051456
Minimums & maximums of grid:
  -3472.551456 - 4185.551456
  -3829.051456 - 3829.051456
  -2579.051456 - 5079.051456

Model minimum & maximum.         X: -3001.000000 to 3714.000000         Y: -1350.000000 to 1350.000000         Z: 0.000000 to 2500.000000

Enter spacing (mm) between fired rays. 10

grid spacing: 10.000000

Shooting down 1st axis.

Shooting down the 2nd axis.

Shooting down the 3rd axis.

SUMMARY OF FILES USED & CREATED         .g file used: test.veh.g         regions used:                 vehicle                 air         file containing second pass information: veh.f.2nd         material file used: prp         conductivity file created: veh.s.con          (format is PRISM 3.0)         conductivity table file created: veh.s.tbl         error file created: veh.s.err

Freeing memory.


1. Made the numbering scheme for regions the same throughout all irprep programs, i.e. region numbers start at one not zero. This affects the format of the diagnostic and error files.

2. Correct the format of the conductivity file for PRISM. The larger region number must come first.

3. The user is given a choice of a 2.0 PRISM format or a 3.0 PRISM format.

4. Some diagnostic information is no longer printed out.

5. The user is given a choice of firing one set of rays or three sets of orthogonal rays.


firpass(1), shapefact(1), all_sf(1), showtherm(1), ir-X(1), ir-sgi(1), pictx(1), pictsgi(1), Users Manual for IRPREP (BRL-SP-96), Computer Programs for Generating an Input File for PRISM and Displaying PRISM Results (BRL report in progress)


Susan A. Coates


This software is Copyright (c) 1991-2013 by the United States Government as represented by U.S. Army Research Laboratory.


Reports of bugs or problems should be submitted via electronic mail to <>.

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BRL-CAD SECPASS (1) 04/04/2016

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