ACIS file format

The 3D ACIS Modeler (ACIS) is a 3D modelling kernel (or engine) owned by Spatial Corporation (formerly Spatial Technology). ACIS is used by many software developers industries such as computer-aided design, (CAD), Computer-aided manufacturing (CAM), Computer-aided engineering (CAE), Architecture, engineering and construction (AEC), Coordinate-measuring machine (CMM), 3D animation, and shipbuilding. ACIS provides software developers and manufacturers the underlying 3D modeling functionality.

ACIS features an open, object-oriented C++ architecture that enables robust, 3D modelling capabilities. ACIS is used to construct applications with hybrid modeling features, since it integrates wireframe model, surface, and solid modeling functionality with both manifold and non-manifold topology, and a rich set of geometric operations.

ACIS can also be used for a 3D CAD file formatting that will allow you to do a FEM on a MRI image.