Class Name: Reference Vector with Location Index

Superclass - Base Reference Vector

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 must 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 meters apart, so they may share a vector. If they are several hundred meters 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 (one-way)(inherited)

• optionally, a Location

Composed of (two-way)(inherited)

• optionally, a Reference Vector Control Link

Component of (one-way)

• one Reference Vector Table

Inherited Field Elements

Field Elements

Notes

Fields Notes

location_index

index into a <Location Table>