DIRSIG

One of the fundamental modules in D5 supplies a model of the earth (or other, roughly ellipsoid planet) to the core representation of the DIRSIG universe. The distributed version of D5 will likely contain a simple, material-mapped sphere representation of the earth by default (to keep download sizes reasonable), with the option to obtain more detailed (and more correct) models. To this end we've been working on an earth model based on the WGS84 reference ellipsoid and SRTM ( Shuttle Radar Topography Mission ) DEM data. Since this is a very large data set (the 500m data we're using currently is 4.7GB in its raw form) it is an ideal case to test some of our new large file handling routines and integrating them into geometry interactions. We model the earth as a collection of triangle mesh patches representing cells (primarily hexagons) of a geodesic, specifically the ISEA aperture 4 resolution 7 grid (i.e. 163,842 index cells). Each patch can be loaded into memory independently,

The transition from DIRSIG 3 to DIRSIG 4 was a major shift towards a more modern code architecture and a more flexible simulation design. The goal was to address the development challenges faced at that time and to be ready for the new features and capabilities that would come. During the past few years, we have added new modalities (particularly LiDAR), new platform support (Windows), an entirely new GUI interface, native 3D radiative transfer code, extensive sensor and platform modeling, support for more complex scene radiometry, and many other features to support user needs. Every new piece of code has expanded, and in some cases, stressed, the underlying DIRSIG 4 framework and its original design. While this evolution has been successful functionally, we have made sacrifices to execution speed and our agility adapting to new challenges and projects well beyond the scope of what was imagined, or even possible, when that framework was constructed. DIRSIG 5 (D5) represents another maj