Representation of 3D modelling

Link : http://en.wikipedia.org/wiki/3D_modeling

As said, 3D models can be seperated into two categories.
They are Solid and Shell/Boundary.

Solid

• Under the solid category. "These models define the volume of the object they represent (like a rock). These are more realistic, but more difficult to build". "Solid models are mostly use for nonvisual stimulation."Quote from the paragraph.(eg medical and engineering simulations)

Shell/Boundary

• The models represent the surface of the object and it's not the volume. "(like an infinitesimally thin eggshell)." Quote from the paragraph. This Shell/Boundary models are easier compared to the solid models.