Class Name: Reference Vector With Location Index

Superclass - <Base Reference Vector>

Subclasses

Definition

A <Base Reference Vector> used in a <Reference Vector Table>. See <Reference Vector>.

<Reference Vector With Location Index> uses an index into a <Location Table> higher in the <Aggregate Geometry> tree to specify a <Location> component (needed for coordinate conversions and transformations).

Primary Page in DRM Diagram:

• 7

Secondary Pages in DRM Diagram:

• 18

Example

See <Reference Vector>.

FAQs

Why is <Location> an optional component?

Because if location_index == SE_COMPONENT_IS_AGGREGATED for a given <Reference Vector With Location Index>, then that object does not obtain its <Location> from a table, but shall aggregate the <Location> directly.

Is the location_index field a 1-based index?

Yes.

How do I pick a <Location> for a shared <Reference Vector With Location Index>?

If the objects sharing the vectors are in an LSR spatial reference frame, then any <Location> (e.g. (0, 0, 0)) will do. If the objects are in any other (i.e. non-LSR) spatial reference frame, then nearby objects may share a "nearby" <Location>. The meaning of "nearby" depends on how important the curvature of the earth is to the data provider. For example, two <Spot Lights> pointing up will have approximately parallel beams if they are a few metres apart, so they may share a vector. If they are several hundred metres apart, then their beams noticeably diverge, so they should not share a vector in that case. (Shared vectors are always parallel.)

See also FAQ in <Reference Vector>.
See also FAQ in Required Reference Vector Location.

Constraints

Composed of (two-way)(inherited)

• zero or one <Location> instance
• zero or one <Reference Vector Control Link> instance

Component of (two-way)

• one <Reference Vector Table> instance

Inherited Field Elements

Field Elements

Notes

Fields Notes

location_index

 index into a <Location Table>