DIRSIG

The new DIRSIG 4.4.2 release includes 10 new demos, bringing the total number of these feature focused simulations to 53. Some of these demos have been briefly discussed in other posts (for example, the expanded Geometry Primitives and Bayer Pattern Focal Plane demos). The following is a list of the new demos in the 4.4.2 release: Bayer pattern focal plane A set of example BRDF materials LIDAR returns from a sloped surface LIDAR returns from sub-pixel structures A geo-synchronous, exo-atmospheric "moon-like" satellite A 4-camera, division-of-aperture polarization system A 2x2 microgrid division-of-array (focal plane) polarization system An expanded set of primitive geometry objects An extended-area, directly viewable source An advanced UV mapping example Like the other demos included with DIRSIG, each demo is a self-contained simulation that can be easily downloaded (from within your local installation), unzip and run without any modifications. We consider t...

Like most ray tracing environments, DIRSIG offers a number of convenient primitive objects to use in place of facetized geometry. Aside from offering a quick way to construct a (simple) scene, primitives have mathematically defined surfaces so there is no reason to worry about edges between facets. In contrast to vertex normal interpolation which helps smooth the appearance of facetized objects, primitives offer true, smooth geometry which can be convenient for working out precise radiometry problems. We've already made some of these primitive objects available under the old object database (ODB) inputs, which has been shown in the PrimitiveObjects1 demo. These objects are shown below. The primitives shown are a box, a sphere, a cylinder, a ground plane, a disk, and a two material disk (introduced to quickly model a Secchi disk for virtually measuring turbidity). We've now updated the "glist" format to support these primitives and to provide previously unavail...

One of the new features that will be in the upcoming DIRSIG 4.4.2 release is something that we have been calling "data-driven focal planes". This mechanism had been on the drawing board for many years and we finally had a reason to implement it on our contract to help model the Landsat Data Continuity Mission (LDCM) sensors, or what many of you will come to know as Landsat 8 when it is launched in December 2012. The concept of the "data-driven" focal plane was to provide an alternative to the parameterized detector array geometry, where you specify the focal length, the number of pixels, the pixel pitch and pixel spacings. Instead a "data-driven" focal plane uses a "database" where each record describes both the geometric and radiometric properties of a single pixel. The key feature is that the geometric and optical properties are described at the front of the aperture. This allows the model to ingest optical predictions from complex optical m...

We've just put together another DIRSIG "demo" simulation. It shows a camera placed indoors. The scene is illuminated by both a secondary source at the ceiling and through a window cut-out at the far end of the room. This demonstration will be included in the next DIRSIG release.

One of the ways we try to teach users about specific features is by making a "bare bones" simulation as a demonstration of that feature. These "demos" don't usually generate a very exciting output data product, but they are fully self-contained (no external data required) simulations that focus on how to configure a specific feature. We have been distributing our growing set of demos with DIRSIG releases for some time. In DIRSIG-4.4.0, we tried to make demos easier to use. The "demos" folder now includes a top-level HTML index file. On a Windows installation, this HTML index is can be opened by clicking the "Demonstrations" item in the "DIRSIG 4" sub-menu of the Start menu. On Mac and Unix/Linux, just open $DIRSIG_HOME/demos/index.html in your browser. This shows a thumbnail image for each demo and gives a brief description of what the example demonstrates. Note the "Download this demo" link under each description. Whe...