All distance calculations are done by the Lod Source.
It acts as a centre point from which the distances to all Lod Objects are calculated.
It’s normally used by cameras, but can be added to any game object which should act as a centre point.

There is no limit of Lod Sources you can use at once.
But similar to lights, each lod source adds another calculation pass for the distance calculation.
It is thus recommended to not to use tons of Lod Sources at once.

Performance

The performance impact of a Lod Source depends on the Lod Manager used.
In general it’s a good idea not to use more Lod Sources than necessary.

With the LodManagerCubic, each Lod Source only affects cells in its update range.
Cells outside the update range are ignored by this Lod Source.
It is thus crucial to choose a good max update distance, see below.

Max Update Distance

The max update distance represents the range in which a Lod Source can update Lod Objects.

As the max update distance has a big impact on performance, it’s critical to choose the optimal value.
The shorter this distance, the better the performance.
You should take some cases into account to choose the best distance value.

  • Largest LOD level distance
    The update distance doesn’t need to be larger than the largest used lod level distance of any Lod Object.
    Using the automated distance calculation takes all Lod Objects in the scene into account and calculates the optimal distance for the scene.
  • Camera view distance
    When the camera view distance is smaller than the largest LOD level distance, you should take the view distance instead.

View angle

In order to reduce the amount of chunks to calculate, you can restrict a Lod Source to a certain view angle. With this restriction, all chunks outside this view angle will be ignored.
This reduces the amount of chunks drastically and improves the update interval for all active chunks a lot.

As a downside, you can have objects popping (sudden appearance of objects) into the screen when you turn around the camera, so this restriction should not be used on fast rotating cameras.
This option is perfect for stationary cameras or cameras with a small field of view.

There are three view angle modes available.
The following summary should help you to choose the best one for your use case.

HardFieldOfViewHard
Uses only the view angle and ignores everything outside it.
This can lead to many visual artefacts and should only be used when this doesn’t matter (surveillance camera, reflection camera, etc.)

  • Fastest mode
  • Best culling behaviour
  • Causes more popping
  • Can lead to artefacts at the screen border

Hard with border FieldOfViewHardWithBorder
Uses the view angle and adds a border to it.
This prevents visual artefacts when the camera doesn’t rotate to fast.
It should be used when the artefacts from the hard mode are obtrusive.

  • Good culling behaviour
  • Prevents most popping
  • Slow
  • Not usable for fast rotating cameras

SmoothFieldOfViewSmooth
This uses a gradual falloff for cells outside the view angle.
It has a poor cell culling behaviour but still better than nothing.
On the other hand it is usable for fast rotating cameras.

  • Usable for fast rotating cameras
  • There’s usually no popping
  • Slow
  • Bad culling behaviour

Camera observation

Some settings in the Lod Source depend on settings in the camera.
When those settings change, the Lod Source settings should also change.

When you know that the camera settings can change, you should activate the camera observation.
This allows the Lod Source to react to any changes made to the camera so that you don’t need to worry about it.

When the Lod Source observes the camera, you can tell it which settings it should manage.
Managed settings cannot be changed directly, as they depend on the camera settings

Local distance multiplier
Depends on the field of view from the camera.
You define a default field of view for which the local distance multiplier is 1.
When the field of view in the camera changes, the local distance multiplier is automatically updated.

View angle
The view angle depends on the field of view and the aspect ratio of the camera.