This paper describes a newly developed 3-D shape modeling system, in which a user can design a free-form surface as if he or she actually manipulates a flexible object made from rubber or clay. Such reality can be realized in the system without any encumbering devices like goggles, glasses, or gloves, which is impossible in conventional virtual reality systems. The system is composed of a volume scanning display for presenting a surface image in a real 3-D space, a multisensory input device for detecting the force for deformation, and a half-silvered mirror for spatial superposition of the image onto the input device. A user can directly manipulate a free-form surface by virtually pushing the image, actually pushing the input device, and at the same time, he or she can feel the input device resist its actual deformation as the resisting force of the virtual surface. The system has several types of deforming models, and two types of free-form surfaces that have different curvatures have been experimentally created.