GetAbsOrigin()

GetAbsOrigin() returns the world co-ordinates of the origin of any point or model entity as a vector. This is theoretically the centre of the object, but for NPCs (to choose a prominent example) will be a point exactly half way between the soles of their feet when in the reference posture, or wherever else the modeller has placed it.

Alternatives

You may want to use a different method of finding an entity's location, particularly given the fact that GetAbsOrigin() will not work with brushes unless they are tied to an entity that creates one for them - which may well not mark the location of the object in any useful way!

Todo: How many of these OBB functions work with vphysics?

WorldSpaceCenter()

Returns the centre of an entity's object-aligned bounding box as a vector.

CollisionProp()->CalcNearestPoint( const Vector &vecWorldPt, Vector *pVecNearestWorldPt )

Calculates the nearest point to vecWorldPt of an entity's object-aligned bounding box.

Note:Instead of returning a value, this function will modify whatever variable is passed for pVecNearestWorldPt.

Todo: More...