This group node is used to allow applications to switch between various representations of objects automatically. The children of this node typically represent the same object or objects at varying levels
of detail, from highest detail to lowest. The distance from the world-space eye point to the transformed center of the LOD is computed, and one child is drawn, based on the values in the ranges field.
More
precisely, if the distance from the world-space eyepoint to the transformed center is D and the ranges array contains LAST_RANGE+1 values (numbered 0...LAST_RANGE), then:
if D < ranges[0] : Child 0 is drawn
else if ranges[i-1] < D < ranges[i] : Child i is drawn
else if D > ranges[LAST_RANGE] : Child LAST_RANGE+1 is drawn
Thus, N ranges and N+1 children
should be specified. If you specify too few children, the last child will be used for the extra ranges. If you specify too few ranges, the extra children will never be used.
It is often useful to define
the lowest detail child to be an
SoInfo node. This causes the object to completely disappear if it is far enough away from the eyepoint. Defining the highest detail child to be an
SoInfo node can also
be useful if you want the object to disappear if it gets too close to the eyepoint.