Thanks, nice to learn more. This gives me input to think about how I can improve in my engine.

@Kalle; just a short update, I've managed to save quite some 'bytes' per bounding box.

Some vectors were just waste (AABBsize == OBBsize), and some are only necessary when creating the AABB, so now I simply created them on the stack.

The 8 AABB corners and OBB corners I still got in place, because I don't know how to 'save them'. Because per frame I transform the AABB corners to OBB corners, to determine the worldpace AABB size. I could probably save that, only if I would cull in local/ modelspace as you suggested.

typedef struct BOUNDINGBOX
{
	D3DXVECTOR3 AABBcenter;
	D3DXVECTOR3 AABBsize;
	D3DXVECTOR3 AABBcorners[8];

	D3DXVECTOR3 OBBcenter;		// OBB in worldspace now
	D3DXVECTOR3 OBBcorners[8];
	
	D3DXVECTOR3 AABBworldsize;	// AABB in worldspace, uses P/N-vertex 

	bool		created;

	BOUNDINGBOX():created(false) { };
} BOUNDINGBOX;