19.6. Frequently Asked Questions

19.6.1. Which versions of DIRSIG support Interactive Mode?

The first version of Interactive Mode appeared in DIRSIG-4.0.8. All current development and feature implementations are being done on the DIRSIG 4.1 branch. The Binary output functionality is not available in the 4.0 series.

19.6.2. Can interactive queries be supplied via a file?

On a UNIX system, interactive queries can be supplied from a file using shell redirection. Here are the contents of a sample request file named "input.txt":

0 1 10 10 100 0 0 -1
0 1 15 20 100 0 0 -1
0 1 80 80 120 0 0 -1
  

The input file can then be supplied to DIRSIG as follows:

    dirsig4 -interactive ./demo.xml texture.cfg < input.txt
  

19.6.3. How can I specify the wavelengths for which Interactive Mode generates output?

With DIRSIG-4.1, the spectral coverage is now specified via a bandpass XML file. See the How-To section for details on the syntax of this input.

19.6.4. Why does the first ray take so long to trace?

DIRSIG uses spatial data structures to speed geometric intersection. The first time a scene is traced, a global spatial sort in to such a data structure takes place. Likewise, the first time any specific piece of geometry is traced a similar sorting occurs. The results of this spatial sort are cached and any future rays will intersect at full speed.

19.6.5. How can I generate an ADB for use with Interactive Mode?

The make_adb utility, starting with the 4.0.9 release, can generate an ADB for a series of Interactive Mode queries specified in a file.