indexing

	description: "[

		Implements support routines for classes of objects which have an orientation.

	]"
	date: "$Date$"
	revision: "$Revision$"

class EM3D_ROTATABLE
inherit
	EM3D_TRANSFORMABLE
feature -- Status


	orientation: EM_QUATERNION is
			-- Describes the local orientation, relative to the parent entity
		do
			result := transformation
		end
	set_orientation (a_orientation: EM_QUATERNION) is
				-- Set `orientation' to `a_orientation'.
		do
			rotate( orientation.inversed * a_orientation )
		ensure
			definition_of_set_orientation: orientation = a_orientation
		end

	rotate(a_rotation: EM_QUATERNION) is
				-- Rotate the object with a quaternion.
		do
			transformation.multiply ( a_rotation )
		end

end