Name
rttherm — raytrace a hyper-spectral thermal image of an mged model
DESCRIPTION
rttherm(1)
is a member of the RTUIF family of programs,
and implements the same options as
rt(1),
with the exception that the
-F
(framebuffer)
option is currently not implemented and reserved for future use.
rttherm(1)
creates a hyper-spectral ray-trace into
the output file
specified with the
-o
option.
It also writes a second file (using bn_table_write) with
the suffix ".spect" which describes
the spectral sampling pattern used when creating the output file.
SPECIFYING TEMPERATURES
Temperatures are always specified in degrees Kelvin ("Kelvins").
The background (ambient) temperature may be set from the command
line with the
-c set bg_temp=degK
command, or in the animation script with the command
set bg_temp=293.0
which is the default. (20 degrees C is 293 degrees Kelvin).
The spectral sampling density may be set from the command line
with the
-c set spectrum=nsamp/lo_nm/hi_nm
option, or in the animation script with the command
set spectrum=nsamp/lo_nm/hi_nm
The default setting is 100/380/12000, which takes 100 samples equally spaced from 380nm (low end of the optical band) to 12microns (upper end of the "Far-IR" band).
rttherm(1) is built using libmultispectral(3) rather than liboptical(3), which provides a similar set of shaders. Most notable is the "temp" shader, which applies a two-dimensional temperature map to a region in exactly the same way as the "texture" and "bwtexture" shaders apply colors to the surface.
The temperature of a region may be modified by the
rt animation script which is read by
rttherm(1)
when the
-M
flag is specified.
The syntax of the anim command is:
anim path temp ## ;
where "anim" is a keyword, "path" is the path specification for the affected combination(s), "temp" is a keyword ("temperature" is also accepted), and ## is the new temperature for the combination(s) in Kelvins.
The Tcl interface to the database supports adjusting region temperatures. The syntax of the anim command is:
db put|adjust combname temp ##
where "db" is the name of the Tcl database object for the desired database (typically "db" or ".inmem"), "put" and "adjust" are keywords, "combname" is the name of the combination, "temp" is a keyword, and ## is the new temperature for the combination in Kelvins. Note that the BRL-CAD v4 database has no place for storing region temperatures on disk, so this command won't have any effect on v4 databases.
POST PROCESSING
ssampview(1) is a GUI tool for viewing the multi-spectral output files created by rttherm(1). In the works is a post-processing tool which will extract a spectral window into a conventional 8-bit/pixel bw(5) file, probably in two steps: (1) extracting a representative power value per pixel into a dbw(5) (double-precision .bw file), and then (2) using cv(1) to perform a direct conversion, or using dpix-pix(1) or similar tool to perform scaling and/or auto-ranging.
