The creation and manipulation of conceptual shapes need different modeling techniques from what are available in present CAD systems. Conceptual modeling techniques are supposed to provide more flexible interaction and mimic working with true materials. Therefore, this paper proposes a new computer internal modeling technique that supports the natural ways of exteriorizing shape concepts as well as their sophisticated geometric representation. The vague shape model consists of three aspect models, the particle system, the physical coupling, and the singularity network models. The discrete particle system model is composed from point sets that are generated with highly interactive input devices. The volumetric and physical manipulations can be applied to the particle clouds. A particle system model is a domain-oriented representation of a cluster of shape instances. To make behavioral simulation possible, physical couplings such as springs and dampers are specified among the particles. The discrete particle system representation can also be converted into continuous surface models based on the extraction of the shape singularities and natural surfaces.