Abstract: In many application problems of CAD/CAM and scientific visualization, the interior and exterior of solids are both needed to be described, but the existing surface modeling technique can only describe the exterior of solids. In the light of this situation, a simple method is presented which can be used to build the volume geometric model of solids from it's surface model. Volume geometric model is a solid model and can be applied in interior visualization of solids and CAD/CAM.