Constructive Solid-Geometry Methods (CSG)
Constructive models represent a solid as a combination of primitive solids. This modeling technique combine the volumes occupied by overlapping 3D shapes using set boolean operations. This creates a new volume by applying the union, intersection, or difference operation to two volumes A and B. which is self-explanatory.
The method of Constructive Solid Geometry arose from the observation that many industrial components derive from combinations of various simple geometric shapes such as spheres, cones, cylinders and rectangular solids. In fact the whole design process often started with a simple block which might have simple shapes cut out of it, perhaps other shapes added on etc. in producing the final design.