The SEDRIS Data Representation Model
APPENDIX A - Classes Spatial Index Related Geometry Topology |
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An instance of this DRM class specifies a spatially indexed (tiled) organization of primitive <Geometry Topology> instances.
The set of all <Geometry Topology> instances contained within an independent topological surface, organized into a collection of regularly shaped tiles.
We need a 'branch', and each branch from an aggregation is a hierarchy object, because <Aggregate Geometry> instances contain <Geometry Hierarchy> instances. When an <Aggregate Geometry> instance has a <Geometry Topology Hierarchy>, that <Aggregate Geometry> represents a distinct topological surface. We shall organize a topological surface, a.k.a. an "independent topology", which eventually, in SEDRIS, is 'rooted at' a single <Aggregate Geometry> instance.
The <Geometry Hierarchy> instances are either <Aggregate Geometry>, or <Property Grid Hook Point>, or or <Geometry Model Instances>. The topological organization of a <Model>, if any, is contained within the <Model>, so we're left with a need to specify the topological organization of an <Aggregate Geometry> instance. The organizing principle shall be applied at the <Aggregate Geometry> level - no lower, no higher.
The same spatial indexing structure can be shared by multiple <Aggregate Geometry> because there could exist multiple classification organizations of the same set of <Geometry Representation>. When a single set of <Geometry Representation> is organized by multiple classification approaches, it's still the same set of <Geometry Representation> being dealt with, and still the same set of <Geometry Node>, <Geometry Edge>, and <Face> instances. Changing the logical organization of the <Geometry Representaiton> has no effect on the spatial organization of the underlying topological primitives. Thus, one spatial organization for a set of topological primitives may be shared by many different organizations (aggregations) of <Geometry Representation> where the <Geometry Representation> are composed of the same spatially organized topological primitives, regardless of which organization the <Geometry Representation> are viewed from.
SE_Geometry_Topology_Level | geometry_topology_level; | (notes) |
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This is the origin of the collection, which is the lower-left corner.
The geometry_topology_level field specifies the level of geometry topology that is present within the hierarchy represented by the given <Geometry Topology Hierarchy> instance.
If the value of the sparse field is SE_FALSE, all column and row entries are present; otherwise one or more entries are not present.
The column_count field is the number of cells along the X axis.
The row_count field is the number of cells along the Y axis.
The column_width field is the length of a cell in the given unit along the X axis.
The row_width field is the length of a cell in the given unit along the Y axis.
The spacing_unit field is the unit of measurement used for the spacing of the spatial index.
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