Texture Name Level of Detail

76 © 2016 Open Geospatial Consortium value 1 to 3 digits, followed by an underscore “_”, and concatenated with the field’s name as per Annex M Volume 2 CDB Core: Model and Physical Structure Annexes. Another directory name is created by concatenating all fields with the underscore character. This character string also forms the Moving Model DIS Code MMDC attribute later defined in section 5.7.1.3.40. Together, these five directories classify CDB Moving Models into a DIS-like structure that looks like this: .\1_Kind\2_Domain\3_Country\4_Category\1_2_3_4_5_6_7\ The above directory structure is used, for instance, by the MModelGeometry dataset later defined in section 3.5.1.

3.3.8.4 Texture Name

Requirement 42 http:www.opengis.netspeccdb1.0coretexture-name The name of 3D model textures SHALL be a character string having a minimum of 2 characters and a maximum length of 32 characters. The first two characters SHALL be alphanumeric. Examples of valid texture names are Brick, M1A2, house, City_Hall, etc. A name such as C-130 is invalid because the second character “-“ is not alphanumeric. Requirement 43 http:www.opengis.netspeccdb1.0coretexture-name -file-name The acronym TNAM SHALL represents the texture name and is used to compose texture file and directory names. The following directory structure SHALL be used by CDB Model texture-related datasets: \A\B\TNAM\ The directory represented by \A corresponds to the first character of TNAM in uppercase. The second directory, \B, corresponds to the second character of TNAM in uppercase. As a result, a texture named “house” will be stored in a directory tree with the following structure: 77 © 2016 Open Geospatial Consortium \H\O\house\

3.3.8.5 Level of Detail

The terms “Level of Detail” and its acronym “LOD” are generally well known to the intended audience of this standard. Requirement 44 http:www.opengis.netspeccdb1.0core lod-file-name In the context of the CDB standard, filenames and directory names SHALL be composed from the concept of LOD. This standard specifies a numeric scale to classify a LOD between 34 levels numbered from −10 to +23. The details will be provided later in the document. At this point, it is sufficient to define the convention used throughout the standard to designate a particular LOD. The standard designates a LOD by appending its level to the uppercase letter L. When the level is negative, the uppercase letter C is used in lieu of the minus sign. The numeric values of all levels are represented by 2-digit numbers. As a result, LODs are designated as LC10 for level −10, L00 for level 0, or L23 for level 23.

3.4 GTModel Library Datasets

Requirement 45 http:www.opengis.netspeccdb1.0core gtmodel-directories The \CDB\GTModel\ folder SHALL be the root directory of the GTModel library which is composed of the following datasets: 1. GTModelGeometry 2. GTModelTexture 3. GTModelDescriptor 4. GTModelMaterial 5. GTModelCMT 6. GTModelInteriorGeometry 7. GTModelInteriorTexture 8. GTModelinteriorDescriptor 9. GTModelInteriorMaterial