This study aims to establish an interactive and intuitive region extraction environment for volume data. A volume clipping method using deformable boundary object is proposed to support 3D region extraction task. Slice-based volume rendering of boundary elements enables to visualize clipped results in real time. Geometrical transformation and physics-based deformation support intuitive modification of 3D region of interest. Some extraction tasks are tested using CT data set on the developed system. All tests confirmed real-time visualization of clipped results is effective for interactive 3D region extraction in volume visualization and virtual object modeling.