Definition

Consider Q that is either an instance of <Quadrant Related Features> <Quadrant Related Geometry>.

1. Q shall have a <Spatial Extent> component.

2. Each branch of Q shall comply with the following constraints.

   1. Each component representing a quadrant shall have a <Spatial Extent> component. In the case of quadrants represented by <Geometry Model Instance> instances or <Feature Model Instance> instances, the <Model> instance being referenced shall have the <Spatial Extent> component.

   2. For each branch of Q, each primitive within the branch shall have a spatial extent fully contained within that specified by the <Spatial Extent> instance corresponding to the branch. Consequently, the unique_descendants field of Q shall be set to SE_TRUE, because no DRM object can be fully contained within the <Spatial Extent> instance of more than one branch of Q.

   3. The regions defined by the branches shall not overlap; that is, the <Spatial Extent> components of the component hierarchies shall not overlap.

   4. The four possible quadrant components' <Spatial Extent> components shall be defined in their native SRF within the area specified by the <Spatial Extent> component of Q as depicted in Figure 5.

      

      Figure 5 — <DRM Quadrant Related Organizing Principle> Quadrant Specification

      Consider the bounding area defined by the <Spatial Extent> component of Q, as divided into four quadrants of equal size.

      1. If a branch with SE_QUADRANT_LEFT_BACK is present, its <Spatial Extent> component shall specify the area of the left back quadrant, such that

         b.4.i.1	its right boundary aligns with the left boundary of the SE_QUADRANT_RIGHT_BACK quadrant's <Spatial Extent> component, if present, and
         b.4.i.2	its front boundary aligns with the back boundary of the SE_QUADRANT_LEFT_FRONT quadrant's <Spatial Extent> component, if present.
         b.4.i.3	In the case where a primitive lies entirely along the right boundary of the branch, the primitive is considered not to lie within the spatial extent of the SE_QUADRANT_LEFT_BACK but within that of the SE_QUADRANT_RIGHT_BACK quadrant.
         b.4.i.4	In the case where a primitive lies entirely along the front boundary of the branch, the primitive is considered not to lie within the spatial extent of the SE_QUADRANT_LEFT_BACK but within that of the SE_QUADRANT_LEFT_FRONT quadrant.

      2. If a branch with SE_QUADRANT_RIGHT_BACK is present, its <Spatial Extent> component shall specify the area of the right back quadrant, such that

         b.4.ii.1	the <Location> instances representing its right back corner corresponds to that of the <Spatial Extent> component of Q;
         b.4.ii.2	its left boundary aligns with the right boundary of the SE_QUADRANT_LEFT_BACK quadrant's <Spatial Extent> component, if present, and
         b.4.ii.3	its front boundary aligns with the back boundary of the SE_QUADRANT_RIGHT_FRONT quadrant's <Spatial Extent> component, if present.
         b.4.ii.4	In the case where a primitive lies entirely along the left boundary of the branch, the primitive is considered to lie within the spatial extent of the SE_QUADRANT_RIGHT_BACK and not within that of the SE_QUADRANT_LEFT_BACK quadrant.
         b.4.ii.5	In the case where a primitive lies entirely along the front boundary of the branch, the primitive is considered not to lie within the spatial extent of the SE_QUADRANT_RIGHT_BACK but within that of the SE_QUADRANT_RIGHT_FRONT quadrant.

      3. If a branch with SE_QUADRANT_LEFT_FRONT is present, its <Spatial Extent> component shall specify the area of the left front quadrant, such that

         b.4.iii.1	the <Location> instances representing its left front corner corresponds to that of the <Spatial Extent> component of Q;
         b.4.iii.2	its right boundary aligns with the left boundary of the <Spatial Extent> component of the SE_QUADRANT_RIGHT_FRONT quadrant, if present; and
         b.4.iii.3	its back boundary aligns with the front boundary of the <Spatial Extent> component of the SE_QUADRANT_LEFT_BACK quadrant, if present.
         b.4.iii.4	In the case where a primitive lies entirely along the right boundary of the branch, the primitive is considered not to lie within the spatial extent of the SE_QUADRANT_LEFT_FRONT but within that of the SE_QUADRANT_RIGHT_FRONT quadrant.
         b.4.iii.5	In the case where a primitive lies entirely along the back boundary of the branch, the primitive is considered to lie within the spatial extent of the SE_QUADRANT_LEFT_BACK and not within that of the SE_QUADRANT_LEFT_FRONT quadrant.

      4. If a branch with SE_QUADRANT_RIGHT_FRONT is present, its <Spatial Extent> component shall specify the area of the northeast quadrant, such that

         b.4.iv.1	its left boundary aligns with the right boundary of the SE_QUADRANT_LEFT_FRONT quadrant's <Spatial Extent> component, if present, and
         b.4.iv.2	its back boundary aligns with the front boundary of the SE_QUADRANT_RIGHT_BACK quadrant's <Spatial Extent> component, if present.
         b.4.iv.3	In the case where a primitive lies entirely along the left boundary of the branch, the primitive is considered to lie within the spatial extent of the SE_QUADRANT_RIGHT_FRONT and not within that of the SE_QUADRANT_LEFT_FRONT quadrant.
         b.4.iv.4	In the case where a primitive lies entirely along the back boundary of the branch, the primitive is considered to lie within the spatial extent of the SE_QUADRANT_RIGHT_BACK and not within that of the SE_QUADRANT_RIGHT_FRONT quadrant.

3. If Q has four branches, the strict_organizing_principle field of Q shall be set to SE_TRUE; otherwise it shall be set to SE_FALSE.

Rationale

1. The quadrant related organization shall provide a <Spatial Extent> component, so that the data provider specifies the bounding area that the quadrant related organization is dividing into quadrants.

2. Each DRM object representing a quadrant shall specify a <Spatial Extent> component, because although quadrants are intended to be of equal size, "size" is not invariant under coordinate transformation. The <Spatial Extent> instances are necessary to ensure that the boundaries between quadrants are well-defined when coordinate conversions and transformations are applied.

3. The <Spatial Extent> instances of the branches and the quadrants that they represent shall correspond.

Example

No example supplied.

FAQs

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