Class Name: Volume Level of Detail Data

Superclass - Level of Detail Data

Definition

Specifies the volume that governs the switching of objects by a Volume-based Level Of Detail Related Geometry or Level of Detail Related Features class.

By default, the branch corresponding to the containing Base Level of Detail Data is switched on when inside the volume and off when outside it. This behavior may be reversed if required.

Primary Page in DRM Diagram:

• 9

Example

1. A runway that needs detail to increase as a viewer reaches 1000 meters from it. A parallelepiped Volume Level Of Detail Data could be defined that is aligned with the runway. It would extend 1000 meters from each edge.
2. A runway that needs detail to increase as a viewer reaches 1000 meters from an end but if the runway is overflown from one side, detail does not need to be switched on until the viewer is 500 meters away. A parallelepiped Volume Level Of Detail could be defined that is aligned with the runway. It would extend 1000 meters from each end but only 500 meters from each side.
3. When a building is entered, everything outside the building needs to be switched off as it can no longer be seen. This can be achieved by containing everything outside the building in a Volume Level Of Detail. The Volume Level Of Detail Data would specify a parallelepiped volume that is the same size as the building and have outside set to true. When the building is entered, the parallelepiped is also entered and the objects outside the building are switched off; they are only on when the viewer is outside the Volume Level Of Detail.

FAQs

Why does Level Of Detail need to be controlled by a volume?

A spherical boundary, defined by a distance from a center point, may not be appropriate for some objects. For example, long, thin objects such as runways. In such cases, Levels Of Detail must be switched at different distances from the center of the object, depending on the direction the object is approached from. A volume allows such a non-spherical boundary to be specified.

Constraints

Composed of (one-way)

• one Location 3D (notes)
• one Volume Extent (notes)
• optionally, a World Transformation (notes)

Component of (one-way)(inherited)

• one or more Base Level of Detail Data

Field Elements

Notes

Composed of Notes

Location_3D

 volume center

Volume_Extent

 volume shape

World_Transformation

 To locate and orient the volume within the currently scoped 'world'
 spatial reference frame

Fields Notes

outside

 If true, indicates that the branch belonging to
 the parent Base Level Of Detail is switched on
 outside the volume.