Table 6.145 — DRM_LOD_Related_Geometry

Property

Description

Class
  • <DRM LOD Related Geometry>

Superclass

Subclass
  • None.

Definition

An instance of this DRM class specifies an aggregation of <DRM Geometry Hierarchy> instances in which each component <DRM Geometry Hierarchy> is an alternate representation of the same entity at a different level of detail. Each component <DRM Geometry Hierarchy> is a collection of <DRM Geometry Representation> instances with a different, possibly overlapping, <DRM Base LOD Data> value, representing alternatives that should be used at different viewing ranges, map scales, spatial resolution, and so on.

The lod_data_type field specifies the subclass of <DRM Base LOD Data> of each link object in the given organization.

Clarifications

1 An association between a <DRM Feature Representation> instance and a <DRM Geometry Hierarchy> instance indicates that the environmental object(s) that they represent have the semantic relationship indicated by the <DRM Base Association Data> instance on the association relationship.

2 An association between two <DRM Geometry Hierarchy> instances indicates that the environmental object(s) that they represent have the semantic relationship indicated by the <DRM Base Association Data> instance on the association relationship.

3 An association between a <DRM Feature Representation> instance and a <DRM Geometry Hierarchy> instance indicates that the environmental object(s) that they represent have the semantic relationship indicated by the <DRM Base Association Data> instance on the association relationship.

4 An association between two <DRM Geometry Hierarchy> instances indicates that the environmental object(s) that they represent have the semantic relationship indicated by the <DRM Base Association Data> instance on the association relationship.

5 An association from a <DRM Hierarchy Summary Item> instance to a <DRM Geometry Hierarchy> indicates that the <DRM Hierarchy Summary Item> summarizes that <DRM Geometry Hierarchy>.

6 An association from a <DRM Reference Surface> instance to a <DRM Geometry Hierarchy> indicates that the <DRM Geometry Hierarchy> organizes the geometric objects that specify the resolution surface of the <DRM Reference Surface>.

7 In the case where multiple <DRM Collision Volume> components are specified for a given <DRM Aggregate Geometry>, the union of the volumes thus specified is used in collision detection.

Class diagram

Figure 6.166 — DRM_LOD_Related_Geometry

Inherited field elements

Field name

Range

Field data type

unique_descendants

 

Boolean

strict_organizing_principle

 

Boolean

Field elements

Field name

Range

Field data type

lod_data_type

 

LOD_Data_Type

Associated to (one-way) (inherited)

Associated to (one-way)
  • None.

Associated by (one-way) (inherited)

Associated by (one-way)
  • None.

Associated with (two-way) (inherited)
  • None.

Associated with (two-way)
  • None.

Composed of (two-way) (inherited)

Composed of (two-way)

Composed of (two-way metadata) (inherited)

Composed of (two-way metadata)
  • None.

Component of (two-way) (inherited)

Component of (two-way)
  • None.

Constraints

Example(s)

  • Consider a <DRM Model> of a house, organized based on viewing ranges. If the viewer is farther away than 1000 metres, the house is not visible. From 500 metres to 1000 metres, the roof and walls are visible but not in great detail. From 0 metres to 500 metres, the windows and door become visible. Consequently, the <DRM Model> is visible at two distance-related levels of detail: 0-500 metres, and 500-100 metres.

    Level of Detail Related Geometry, Example 1

    Figure 6.167 — <DRM LOD Related Geometry> example

    For the more detailed 0,0 - 500,0 metres, different “wall” <DRM Model> instances are instanced for the walls containing the windows and doors; otherwise, the structure of the two levels, for this example, is similar.

  • Three <DRM Model> instances representing a given building are created, each with different <DRM Polygon> counts. The most accurate representation is useful up to a viewing distance of 1 kilometre, the second from 1 kilometre to 2 kilometres, and the third for 2 kilometres to 5 kilometres.

    To indicate this, a fourth <DRM Model> instance can be created as follows:

    Level of Detail Related Geometry, Example 2

    Figure 6.168 — <DRM LOD Related Geometry> example