DIRSIG

Although we will be devoting more time to this topic in the blog, many of you are aware that the next generation version of DIRSIG (aka DIRSIG5) has been under development for the past 2 years. This was a ground-up, restart from zero, etc. effort that establishes the DIRSIG modeling toolkit for the next decade. New core, new approach Although we have developed a compatibility layer to allow existing DIRSIG4 simulations to run, the DIRSIG5 model is radically different under the hood. The lightweight and highly optimized radiometry core uses a different numerical radiometry (light transport) approach than we used in DIRSIG4. In addition to being faster (less work to get an accurate answer) this algorithm is far better suited for parallelization. As a result, we have implemented micro-scale parallelization (multi-threading on multi-core CPUs) from the start and work on macro-scale parallelization (MPI distribution on cluster-style computing) is getting underway. This radiometry core al...

It has been a pretty exciting year for the team at Spectral Sciences, Inc.  with the release of MODTRAN6 . This latest version marks a major milestone in the continued development of one of the most popular and trusted codes for simulating radiative transfer in the atmosphere. In addition to important science related advancements, this latest code also includes significant improvements to the general usability of the software. This includes a new graphical user interface (GUI) and the introduction of a formal application programmer interface (API), which let's codes like DIRSIG interact with MODTRAN in a far more robust way than previous versions allowed. New MODTRAN, new interfaces The major development in the interface area is a shift from the old "tape5" style inputs to a new JSON (JavaScript Object Notation) style input. In addition to improving the general readability of the input, the JSON document format is much easier to read in, modify and write back out. The...

After a 5-year hiatus, we have decided to revive the DIRSIG blog in an effort to increase communication with the DIRSIG user community. We get a lot of emails asking the same questions and it would be a lot easier if we wrote up the answers to these questions and published them in an easy to find location. But the primary reason for that is that there is a lot going on these days and we want to tell everyone about it. Over the next few weeks and months our goal is to try and get everyone up to speed on important developments in DIRSIG land. Specifically, we will start getting everyone up to speed on DIRSIG5, which is the rewrite of DIRSIG4 that uses a new numerical radiometry approach and leverages multi-threading and multi-processing (compute clusters). We are also discuss our progress on GPU-acceleration of some key parts of the DIRSIG calculation (spoiler alert, it is incredibly difficult to migrate an entire code like DIRSIG to the GPU). It should also be noted that DIRSIG5 has ...