Methods and systems for separating a 3D liver object are disclosed. A 3D liver object and selected associated vascular and other anatomic structures are displayed in a 3D space which is rendered on a 2D display screen. One or more 3D separating surfaces are placed in the 3D space based on anatomic structural landmarks that are segmented automatically or interactively, where each of the 3D separating surfaces intersects with the 3D liver object at a corresponding 3D pose. The 3D liver object into at least two sub-segments based on the 3D separating surfaces, which can be individually and independently adjusted directly in the 3D space, in real-time, and interactively by a user based on 3D and/or 2D information related to the 3D liver object, and the selected associated vascular and other anatomic structures.
