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The SEDRIS Data Representation Model
APPENDIX A - Classes Reference Vector With Location Index |
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An instance V of this DRM class is a <Base Reference Vector> specialized for use within a <Reference Vector Table>, such that V specifies an index into a <Location Table> LT to specify V's <Location> component.
LT by necessity is attached higher in the <Aggregate Geometry> object tree in which the given <Reference Vector Table> instance appears.
See <Reference Vector>.
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.
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>>.
| SRM_Vector_3D | unit_vector; | |
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| SE_Reference_Vector_Type | vector_type; |
| SE_Integer_Unsigned | location_index; | (notes) |
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If specified, this is a 1-based index into a <Location Table> instance.
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