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means to produce interesting and entirely predictable lighting effects without resorting to computationally intensive local light sources.
The light map adds to the lighting levels provided by the simulated ambient light level; the combined ambient lighting and the light map together modulate the underlying VSTI. Light
maps can be created in a number of ways, either manually with a tool such as Photoshop, from night-time imagery or finally from an off-line rendering process that simulates the illumination
effect of the urban lighting sources onto the terrain.
Requirements Class - VSTLM 103 req
coretiled-raster-vstlm Target type
Operations Dependency
Various XML schema Requirement 103
req
core
vstlm-component-data-type
5.6.2.4.1 Data Type
Requirement 103
http:www.opengis.netspeccdb1.0core vstlm-component-data-type
The VSTLM component SHALL be represented as single-channel gray-scale images, or as triple-channel color images. The data SHALL be stored in JPEG 2000 format. Note
that in the case of a monochrome VSTLM, the implied chrominance of the VSTLM is white.
5.6.2.4.2 Default Read Value
Simulator client-devices should default the VSTLM values if the data values are not available files associated with the VSTLM dataset for the area covered by a tile, at a given LOD or
coarser, are either missing or cannot be accessed. The default value can be found in \CDB\Metadata\Defaults.xml and can be provided to the client-devices on demand. In the case
where the default value cannot be found, the CDB standard recommends that client-devices use a default value of zero-intensity 0.0. Note that the default values are expressed as floating-point
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numbers ranging from 0.0 to 1.0. This ensures that the default is interpreted in a consistent manner independently of its representation in the .jp2 file. The default values are:
● Default_VSTLM_Mono ● Default_VSTLM_Red
● Default_VSTLM_Green ● Default_VSTLM_Blue
5.6.2.4.3 Default Gamma Correction
The default gamma correction is defined by Default_Imagery_Gamma found in the Defaults.xml metadata file. If Default_Imagery_Gamma is not found in Defaults.xml, or if Defaults.xml is not
found in the metadata directory, assume a default gamma correction of 1.0.
5.6.2.4.4 Default Write Value
The files associated with the VSTLM component for area covered by a tile at a given LOD need not be created if the source data is not available. Tiles partially populated with data are not
permitted.
5.6.2.4.5 Supported Compression Algorithm
The CDB standard supports compressed form using the JPEG 2000 format.
5.6.3 Tiled Raster Material Dataset
Historically, Digital Feature Analysis DFAD and VPF Vector Product Format data have been used to provide the terrain and cultural content information used by the real-time sensors, the
computer generated forces and the visual systems. The vectorized outlines of areas tagged with attribution data had a cartoon-like appearance because they did not capture the richly varying
mixture of materials. Each geometric shape would be represented as a single material type resulting in simplistic sensor scenes. Sometimes, a locally applied texture pattern would be
applied to add some realism to the single material type. While it is still possible to build a CDB compliant data store in this manner, the preferred approach involves the use of the Raster
Material Dataset described here. The Raster Material Dataset can be readily derived from the image classification of mono, color or multispectral imagery. This Dataset is a material-coded
image. It is independent of wavelength visible, infrared, etc. and is designed to support geospecific, multi-spectral scene simulation across any computing platform. The Raster Material
Dataset is typically generated from material classification and mixturing analysis see Figure 5- 26: Image Classification Example. It can be developed directly from geospecific imagery, e.g.,
SPOT, Landsat and have a one-to-one correspondence with the image data. The Raster Material Dataset results in a smoothly varying simulation data store free of hard edges characteristically
found in vectorized DFAD outlines.
