Abstract: A method for identifying a target region of a three-dimensional object in a two-dimensional image using a predetermined three-dimensional computer model which includes a number of main features of the three-dimensional object. The method includes designating the target region on the computer model, capturing a real scene which includes at least part of the three-dimensional object, displaying a two-dimensional representation of the real scene together with a view of the computer model, and allowing a user to manipulate the computer model by sizing, translating, or rotating. A view of the computer model and a partial view of the three-dimensional object are superimposed, in order to identify the target region in the two-dimensional representation.