Table 6.128 — DRM_Level_Of_Detail_Related_Geometry

Property

Description

Class
  • <DRM Level Of Detail Related Geometry>

Superclass

Subclass
  • None.

Definition

An instance of this DRM class is an aggregation of <DRM Geometry Hierarchy> objects 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> objects with a different, possibly overlapping, <DRM Base Level Of Detail Data> value, representing alternatives that should be used at different viewing ranges, map scales, spatial resolution, and so on.

Class diagram

Figure 6.148 — DRM_Level_Of_Detail_Related_Geometry

Inherited field elements

Field name

Range

Field data type

unique_descendants1

 

Boolean

strict_organizing_principle2

 

Boolean

Field elements

Field name

Range

Field data type

lod_data_type

 

LOD_Data_Type

Associated to (one-way) (inherited)
  • None.

Associated to (one-way)
  • None.

Associated by (one-way) (inherited)

Associated by (one-way)
  • None.

Associated with (two-way) (inherited)

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

Clarifications

1 If this value is TRUE, each “descendant” of this aggregation - that is, each <DRM Geometry> instance that exists in the component tree rooted at the given <DRM Aggregate Geometry> - shall be unique, in the sense that it shall appear in only one “branch” of this aggregation. If unique_descendants is FALSE, at least one <DRM Geometry> instance appears in more than one “branch” of the aggregation.

2 If this value is TRUE, each “branch” of this aggregation strictly complies with the organizing principle for its particular subclass. If this value is FALSE, at least one “branch” does not strictly comply with the given organizing principle. See the organizing principle constraint for each specific subclass for details.

3 An association between a <DRM Geometry Hierarchy> instance and a <DRM Feature> instance indicates that the <DRM Geometry Hierarchy> and the <DRM Feature> are alternate representations of the same environmental object.

4 An association between two <DRM Geometry Hierarchy> instances indicates that they are alternate representations of the same environmental object.

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.

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 2 distance-related levels of detail: 0-500 metres, and 500-100 metres.

    Level of Detail Related Geometry, Example 1

    Figure 6.149 — <DRM Level Of Detail 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 6.150 — <DRM Level Of Detail Related Geometry> example