Definition

For any oct tree-related organization OTRA, whether an <Oct Tree Related Geometry> or an <Oct Tree Related Features>,

1. The organization shall have a <Spatial Domain> component, defining the bounding volume that the oct tree is organizing into octants. Since a volume is being specified, this <Spatial Domain> shall be specified in terms of <Location 3Ds>.



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

   2.1	Each component representing an octant shall have a <Spatial Domain> component, specified in terms of <Location 3Ds>. In the case of octants represented by <Geometry Model Instance> or <Feature Model Instance> instances, the <Model> being referenced shall have the <Spatial Domain>.
   2.2	Each octant's <Spatial Domain> is distinct from that of all of its siblings, such that they do not overlap or intersect, except that they may have a common boundary.
   2.3	Consider the bounding volume defined by the <Spatial Domain> of OTRA, as divided into 8 octants of equal size in their native SRF.




3. The strict_organizing_principle and unique_descendants field values of OTRA shall be SE_TRUE.

Rationale

1. The oct tree-related organization shall provide a <Spatial Domain>, so that the data provider specifies the bounding volume that the oct tree is dividing into octants.
2. Each component representing an octant shall specify a <Spatial Domain>, because although octants are intended to be of equal size, "size" is not invariant under coordinate transformation. The <Spatial Domains>, are necessary to ensure that the boundaries between octants are well-defined when coordinate conversions and transformations are applied.
3. The <Spatial Domain> instances of the branches and the octants that they represent shall correspond.
4. These <Spatial Domain> instances shall be 3D, because the concept of an oct tree is inherently 3D.

Example

FAQs

Why specify a <Spatial Domain> for each branch of an Oct Tree? Aren't the octants of equal size?

'Size' is not invariant under coordinate transformation.