3d models losing their parts

In several games, you see 3D models getting shot at different par开发者_JS百科ts of their bodies and losing those parts.

What kind of 3D model or what kind of technology they are using?

This is generally achieved by the physical engine. The feature name is usually something like "soft body", or "fracturing soft body". It is a general physical simulator that allows to simulate stuff like clothing, flags in the wind, and, well, dead peoples.

The Havok physical engine is having features to deal with soft bodies, with the Havok Cloth module. You can see a demonstration video of dismemberment here.

Usually, physical engines are working independently from the rendering engine, and also, using their own internal representation of meshes, optimized to their use cases (which are quite different than for rendering). Also, the raw file format of meshes on the disk are usually not used straight as they are, so the file format is usually not relevant to the physical engine (or even to the rendering engine).