Your finite element model may be categorized as being 2D or 3D, and as being composed of point elements, line elements, area elements, or solid elements. Of course, you can intermix different kinds of elements as required (taking care to maintain the appropriate compatibility among degrees of freedom). For example, you might model a stiffened shell structure using 3D shell elements to represent the skin and 3D beam elements to represent the ribs. Your choice of model dimensionality and element type will often determine which method of model generation will be most practical for your problem.

LINE models can represent 2D or 3D beam or pipe structures, as well as 2D models of 3D axisymmetric shell structures. Solid modeling usually does not offer much benefit for generating line models. They are more often created by direct generation methods.

2D SOLID analysis models are used for thin planar structures (plane stress), "infinitely long" structures having a constant cross section (plane strain), or axisymmetric solid structures. Although many 2D analysis models are relatively easy to create by direct generation methods, they are usually easier to create with solid modeling.

3D SHELL models are used for thin structures in 3D space. Although some 3D shell analysis models are relatively easy to create by direct generation methods, they are usually easier to create with solid modeling.

3D SOLID analysis models are used for thick structures in 3D space that have neither a constant cross section nor an axis of symmetry. Creating a 3D solid analysis model by direct generation methods usually requires considerable effort. Solid modeling will nearly always make the job easier.