Class

• <DRM Distance LOD Data>

Superclass

• <DRM Base LOD Data>

Subclass

• None.

Definition

An instance of this DRM class specifies a level of detail described in terms of distance from the eyepoint to the centre of the object.

For each <DRM Distance LOD Data> instance, when moving the eyepoint away from the centre of the object, the representation begins to appear at minimum_range. The representation gradually gets stronger until it is fully visible at minimum_range + minimum_fade_band. As the eyepoint continues to move away from the centre of the object, the representation gradually starts to fade out at maximum_range - maximum_fade_band until it completely disappears at maximum_range. If fade bands are specified, adjacent levels shall overlap within those fade bands and not overlap any other portion of the adjacent level(s).

The minimum_range field is specified in metres as the minimum distance from the centre of the object.

The minimum_fade_band field is expressed in metres relative to the minimum_range value. This fade band is defined to be adjacent to the minimum_range and further from the centre of the object.

The maximum_range field is specified in metres as the maximum distance from the centre of the object. +∞ is a legal range value.

The maximum_fade_band field is expressed in metres relative to the maximum_range value. This fade band is defined to be adjacent to the maximum_range and closer to the centre of the object.

Class diagram

Figure 6.64 — DRM_Distance_LOD_Data

Constraints

• LOD related organizing principle
• Publishable object

Example(s)

• Consider a <DRM LOD Related Geometry> instance that has two branches, each through a <DRM Distance LOD Data> link object as depicted in Figure 6.65:

  

  Figure 6.65 — <DRM Distance LOD Data> example

  The first <DRM Distance LOD Data> link object has:

  minimum_range	100,0
  minimum_fade_band	10,0
  maximum_range	200,0
  maximum_fade_band	20,0

  The second <DRM Distance LOD Data> link object has:

  minimum_range	200,0
  minimum_fade_band	10,0
  maximum_range	1000,0
  maximum_fade_band	10,0

  If the eyepoint is moving outward and the distance reaches 90, the first branch starts fading in. At a distance of 100, the first branch has totally faded in. At a distance of 180 the first branch starts to fade out. At a distance of 190 the second branch starts fading in. The first and second branches are both seen (superimposed) between the ranges of 190 and 200. At a distance of 200 the first branch is totally faded out, while the second branch is the only branch seen. At a distance of 990, the second branch starts fading out, and at 1000 it is completely faded out.

• Consider a <DRM LOD Related Geometry> instance which has two branches, each through a <DRM Distance LOD Data> link object.

  The first <DRM Distance LOD Data> link object has:

  minimum_range	50,0
  minimum_fade_band	20,0
  maximum_range	100,0
  maximum_fade_band	30,0

  The second <DRM Distance LOD Data> link object has:

  minimum_range	110,0
  minimum_fade_band	15,0
  maximum_range	500,0
  maximum_fade_band	10,0

  If the eyepoint is moving outward and the distance reaches 30, the first branch starts fading in. At a distance of 50, the first branch has totally faded in. At a distance of 70 the first branch starts to fade out. At a distance of 95 the second branch starts fading in. The first and second branches are both seen (superimposed) between the ranges of 95 and 100. At a distance of 100, the first branch is totally faded out, while the second branch is the only branch seen, but has not completely faded in. At a distance of 110 the second branch has completely faded in. At a distance of 490 the second branch starts fading out, and at 500 is completely faded out.

• A set of polygonal data is produced with low detail for viewing at ranges greater than 3200 metres, and organized as a <DRM Union Of Primitive Geometry> instance, with a <DRM Distance LOD Data> component specifying this viewing range so that the intended viewing distance at which these <DRM Polygon> instances are to be used is provided.

• See examples for <DRM LOD Related Geometry>.