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The SEDRIS Data Representation Model
APPENDIX A - Classes Union Of Primitive Geometry |
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An instance of this DRM class is a <Union Of Geometry> that is composed of solely of <Primitive Geometry>.
To ensure that the necessary rendering order is followed, the data provider creates a <Union Of Primitive Geometry> UPG, and attaches each <Polygon> as a component of UPG, in order of increasing relative rendering priority (the <Polygon> with the lowest relative rendering priority is attached first).
After all the <Polygon> instances in the underlying layer have been attached, the decal <Polygon> instances are processed in the order in in which they will be rendered.
If a specific method is used for the ordering, the data provider specifies it in UPG's ordering_reason field. In this case, the data was created for a Z-buffered rendering system that supports layers, so ordering_reason is set to SE_ORDRNG_REASON_LYR_HIGH_QUALITY_RENDERING.
A 10 kilometre by 20 kilometre triangulated irregular network of <Polygon> instances.
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| SE_Boolean | unique_descendants; | (notes) |
|---|---|---|
| SE_Boolean | strict_organizing_principle; | (notes) |
| SE_Ordering_Reason | ordering_reason; |
An association between a <Geometry Hierarchy> instance and a <Feature> instance indicates that the <Geometry Hierarchy> and the <Feature> are alternate representations of the same environmental object.
An association between two <Geometry Hierarchy> instances indicates that they are alternate representations of the same environmental object.
An association from a <Hierarchy Summary Item> instance to a <Geometry Hierarchy> indicates that the <Hierarchy Summary Item> summarizes that <Geometry Hierarchy>.
An association from a <Reference Surface> instance to a <Geometry Hierarchy> indicates that the <Geometry Hierarchy> organizes the geometric objects that specify the resolution surface of the <Reference Surface>.
In the case where multiple <Collision Volume> components are specified for a given <Aggregate Geometry>, the union of the volumes thus specified is used in collision detection.
If this value is SE_TRUE, each 'descendant' of this aggregation - that is, each <Geometry> instance that exists in the component tree rooted at the given <Aggregate Geometry> - shall be unique, in the sense that it shall appear in only one 'branch' of this aggregation. If unique_descendants is SE_FALSE, at least one <Geometry> instance appears in more than one 'branch' of the aggregation.
If this value is SE_TRUE, each 'branch' of this aggregation strictly complies with the organizing principle for its particular subclass. If this value is SE_FALSE, at least one 'branch' does not strictly comply with the given organizing principle. See the organizing principle constraint for each specific subclass for details.
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