Table 6.290 — DRM_Union_Of_Primitive_Geometry

Property

Description

Class
  • <DRM Union Of Primitive Geometry>

Superclass

Subclass
  • None.

Definition

An instance of this DRM class is a <DRM Union Of Geometry> that is composed of solely of <DRM Primitive Geometry>.

Class diagram

Figure 6.348 — DRM_Union_Of_Primitive_Geometry

Inherited field elements

Field name

Range

Field data type

unique_descendants1

 

Boolean

strict_organizing_principle2

 

Boolean

union_reason

 

Union_Reason

ordering_reason

 

Ordering_Reason

Field elements

Field name

Range

Field data type

None

    

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)

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 typical geometric representation of an airport runway, in which the runway surface is represented by a layer of polygons, overlaid by stripes (decal polygons).

    To ensure that the necessary rendering order is followed, the data provider creates a <DRM Union Of Primitive Geometry> UPG, and attaches each <DRM Polygon> as a component of UPG, in order of increasing relative rendering priority (the <DRM Polygon> with the lowest relative rendering priority is attached first).

    After all the <DRM Polygon> instances in the underlying layer have been attached, the decal <DRM Polygon> instances are processed in the order in in which they will be rendered.

    If a specific method is used for the ordering, the data provider specifies it in UPG's ordering_reason field. In this case, the data was created for a Z-buffered rendering system that supports layers, so ordering_reason is set to LYR_HIGH_QUALITY_RENDERING.

  • A 10 kilometre by 20 kilometre triangulated irregular network of <DRM Polygon> instances.