The simplest solid objects used for the representation are called **primitives**. Typically they are the objects of simple shape: cuboids, cylinders, prisms, pyramids, spheres, cones. The set of allowable primitives may be restricted; e.g., curved shapes may be forbidden.

It is said that an object is **constructed** from primitives by means of allowable **operations**, which are typically Boolean operations on sets: union, intersection and difference.

This technique operates somewhat differently from polygonal modelling, in which objects are approximated using a series of polygons. Its main application area is CAD.

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2 Applications of CSG |

In modelling packages, basic geometric objects such as the cube or 'box', sphere or ellipse, torus, and a number of other shapes that can be described using a mathematical formula, are commonly known as *primitives*. These objects can typically be described by a procedure which accepts some number of parameters; for example, a sphere may be described by the coordinates of its center point, along with a radius value.

Here, we see that a portion of the blue sphere has been sliced away from the red cube.

Constructive solid geometry has a number of practical uses. It is used in cases where simple geometric objects are desired, or where mathematical accuracy is important. The "Unreal" game engine uses this system.