Level of Detail displays one child of a level of detail group, depending on either the group’s distance to a camera, or based on a screen height percentage.
For LOD groups linked to perspective cameras using a threshold based on Distance, this means measuring the distance between the camera position to the center of the bounding box of the group.
For orthographic cameras, the distance is measured differently. This is because zooming, panning, and dollying in an orthographic view does not change the camera position, but instead changes the camera’s orthographic width. So the distance is measured as:
distance = (default camera distance) * (camera’s orthographic width)/(default orthographic width)
Substituting Maya’s default values in this equation results in the following:
distance = 3.333 * (camera’s orthographic width)