The SEDRIS Data Representation Model
APPENDIX A - Classes
Union Of Primitive Geometry

Class Name: Union Of Primitive Geometry

Superclass - <Union Of Geometry>

Subclasses

This DRM class is concrete and has no subclasses.

Definition

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

Primary Page in DRM Diagram:

Secondary Pages in DRM Diagram:

Example

  1. Consider a 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 <Union Of Primitive Geometry> instance U and attaches each <Polygon> instance as a component of U, in order of increasing relative rendering priority. The <Polygon> instance with the lowest relative rendering priority is attached first. After all the <Polygon> instances in the underlying pavement have been attached, the <Polygon> instances used to decal the pavement are attached in the order in which they will be rendered.

    If a specific method is used for the ordering, the data provider specifies it in the ordering_reason field of U. In this case, the data was created for a Z-buffer rendering system that supports layers, so ordering_reason is set to SE_ORDREAS_LAYERED_HIGH_QUALITY_RENDERING.

  2. A <Union Of Primitive Geometry> instance is a collection of <Polygon> instances making up the representation of a fire hydrant.

  3. A <Union Of Primitive Geometry> instance is a 10 kilometre by 20 kilometre triangulated irregular network of <Polygon> instances.

FAQs

No FAQs supplied.

Constraints

Associated to (one-way) (inherited)

Associated by (one-way) (inherited)

Composed of (two-way) (inherited)

Composed of (two-way)

Composed of (two-way metadata) (inherited)

Component of (two-way) (inherited)

Component of (two-way)

Inherited Field Elements

SE_Boolean unique_descendants; 9
SE_Boolean strict_organizing_principle; 10
SE_Union_Reason union_reason; 11
SE_Ordering_Reason ordering_reason; 12

Notes

Associated to Notes


Feature_Representation

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


Geometry_Hierarchy

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

Associated from Notes


Feature_Representation

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


Geometry_Hierarchy

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


Hierarchy_Summary_Item

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


Reference_Surface

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

Composed of Notes


Collision_Volume

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


LSR_Transformation

An <Aggregate Geometry> instance can have an <LSR Transformation> component only when the <Aggregate Geometry> instance is within the scope of an LSR 3D SRF.

Fields Notes

unique_descendants

If the value of the unique_descendants field is SE_TRUE, each descendant of this aggregation, that is, each <Geometry Representation> instance that exists in the component tree rooted at the <Aggregate Geometry> instance shall be unique, in the sense that it shall appear in only one branch of this aggregation. If unique_descendants is SE_FALSE, at least one <Geometry Representation> instance appears in more than one branch of the aggregation.

strict_organizing_principle

If the value of the strict_organizing_principle field is SE_TRUE, each branch of this aggregation strictly complies with the organizing principle for its particular subclass. If this value is SE_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.

union_reason

The union_reason field specifies the reason why the <Union Of Geometry> instance was created to organize its components.

ordering_reason

The ordering_reason field specifies whether the ordering of the <Geometry Representation> components of the <Union Of Geometry> instance is semantically significant and, if so, what that significance is.


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Last updated: July 26, 2006 Copyright © 2006 SEDRIS