Material Library

Physics-based signature prediction starts with material-encoded scene geometry. SigSim employs a Material Systems Concept to facilitate physical property attribution throughout the synthetic environment to support physics-based signature phenomenology modeling.  It enables the “packaging” and assignment of appropriate physical property data needed for signature synthesis from any scene element.  It has been adopted by the Synthetic Environment and Data Representation and Interchange Specification (SEDRIS) Program’s Environmental Data Coding Specification (EDCS) and is being considered for implementation as a SEDRIS-originated ISO standard for sensor simulation.

Examples of Material Systems include oak-bark-over-living-wood, camouflage-painted-armor-plating-on-insulated-crew-compartment, or grassy-field-over-topsoil-over-clay.

 Material System Concept 

 Material = Homogenous composition of matter with specific values of intrinsic (context-independent) physical properties

 Layer = 1 or more materials, each of arbitrary aggregate mass % in the layer

 1D Material System = Set of layers of arbitrary thickness, with context-dependent boundary conditions

 Provides "hook" for physical property attributions throughout the terrain

 Concept incorporated in EDCS

In this design, a Material System (MS) is a 1-dimensional, N-layered set of raw material compositions, with context-dependent thermal boundary conditions at its top and bottom layers. Each layer is of a specified thickness, and is comprised of a raw material, specified by its own data file of intrinsic (i.e. not context-dependent) physical properties. These include Bulk Properties: Density, Thermal Conductivity, Specific Heat, Latent Heats of Fusion, Evaporation, & Sublimation, Solar Absorptivity, Lambertian Emissivity, etc.; and Spectral BRDF surface parameters, such as directional-hemispherical reflectance (DHR), specularity, and width of the specular lobe, at each wavelength bin.

Each material file has 0.3-16.0 µm spectral DHR, 0-3.0 µm-integrated solar absorptivity and 3-16.0 µm long-wave emissivity, density, specific heat, thermal conductivity and Ulaby-Dobson polarized radar reflectivity parameters for radar. It also has fields for parameterized BRDF model measurements.

The advantage to the 1D Material System approach is that it enables instantiation of the same intrinsic properties to multiple locations on the terrain or cultural feature geometry, while still allowing context-dependent, angle-dependent irradiance loading, thermal calculation, and reflection to occur for each texel independently, by supplying the GPU shaders with the appropriate coefficients of these phenomena’s parameterized models.

For validation of predicted signatures and measurement of spectral material properties for use in research and in support of our signature-prediction products, JRM maintains a material measurement laboratory where these properties can be measured directly. In this laboratory, JRM employs a pair of state-of-the-art spectrometers covering the 0.35 to 16µm spectrum at high spectral resolution.  These devices have digital control and readout laptop computers, and can be mounted for field as well as laboratory use.

Our Material Library is in a format directly consumable by our SigSim spectral signature prediction library. In fact, SigSim and our material library are two key technologies in JRM's GenesisMC Semi-automated Material Classification Tool.

Material Library List