Class Name: Vertex With Component Indices

Superclass - <Base Vertex>

Subclasses

Definition

A specialization of the <Base Vertex> class, used to indicate that one or more of the < Base Vertex>'s components are contained within a <Hierarchical Table> instance found higher in the aggregation tree of the transmittal, and are thus referred to by "component index" rather than by direct attachment to the < Vertex With Component Indices>.

The purpose of this specialization is to make reuse and sharing of these components explicit, by placing them in appropriate <Hierarchical Table> instances for reference by indexing rather than direct aggregation.

Each index field value of a < Vertex With Component Indices> instance is either a sentinel value, SE_COMPONENT_IS_AGGREGATED, or an index into some table.

1. In lieu of a valid index value, an index field may be set to the sentinel value SE_COMPONENT_IS_AGGREGATED, which indicates that the corresponding component is not a reference to a table.

   This sentinel is used both for cases where the < Vertex With Component Indices> instance has no components of the specified class, and where it directly references such components rather than referring to some <Hierarchical Table>.

2. An index field may be an actual index into the collection of <Hierarchical Table> instances which lie above the < Vertex With Component Indices> in the aggregation tree. An index is resolved to an actual component by traversing up the aggregation tree until the correct subclass of <Hierarchical Table> (with respect to the particular index being evaluated) is encountered, such that the span of the <Hierarchical Table> instance includes the index being evaluated. If the <Hierarchical Table> does span the index being evaluated, then its start_index is used to determine which of its ordered components corresponds to the requested index.

Note that for component relationships defined with a cardinality of 0..N, the corresponding subclasses of < Hierarchical Table> accomodate this cardinality, the corresponding <Hierarchical Table> subclasses may aggregate a "set" of target components as well as individual instances.

Primary Page in DRM Diagram:

• 18

Secondary Pages in DRM Diagram:

Example

1. A producer of a transmittal wants to reuse the <Location> instances for <Vertices> of a group of <Polygons>. One possible construction is given below.
   

FAQs

Where can I find further information on the <Hierarchical Table> mechanism?

In addition to the documentation for < Hierarchical Table> and its subclasses, see Part 4, Volume 7 Hierarchical Table Technical Guide of the SEDRIS Documentation Set.

Why is <Location> an optional component of < Vertex With Component Indices>?

Because if location_index == SE_COMPONENT_IS_AGGREGATED for a given < Vertex With Component Indices>, then the < Location> shall be aggregated directly, rather than obtained from a table.

Are the index fields 1-based indices?

Yes; they are defined as unsigned integers only so that sentinel values may be used to indicate when they are not applicable.

Constraints

• <<Image Mapping Functions and Texture Coordinates>>

Associated with (two-way)(inherited)

• zero or one <Geometry Node> instance

Composed of (two-way)(inherited)

• zero or more <Colour> instances
• zero or one <Conformal Behaviour> instance
• zero or one <Morph Point> instance
• zero or more <Property Table Reference> instances
• zero or one <Reference Vector> instance
• zero or more {ordered} <Texture Coordinate> instances

Composed of (two-way)

• zero or one <Location> instance

Component of (two-way)(inherited)

• zero or more <Arc> instances
• zero or more <Finite Element Mesh> instances
• zero or more <Line> instances
• zero or more <Polygon> instances

Inherited Field Elements

Field Elements