Hit Test Types
The following are the various type of hit testing:
HITTYPE_POINT
Hit test by a single pick point.
HITTYPE_BOX
Hit test by a rectangular area.
HITTYPE_CIRCLE
Hit test by circular selection area.
HITTYPE_FENCE
Hit testing by an arbitrary polygon fence.
HITTYPE_SOLID
Hit test a face as if it was solid (even in wireframe mode). Treating an item as solid means the face will be hit if the mouse is anywhere inside the face region and not just over a visible edge. For example in 3ds max when an object is not selected and you put the mouse over it to select it, you need to put it over the wireframe. When an object is selected however you can put the mouse anywhere over the object and the system still considers this a valid area for hit testing. This later case is treating the faces of the selected object as solids.