### 3.3.1 What is CSG?

CSG stands for Constructive Solid Geometry. POV-Ray allows us to construct complex solids by combining primitive shapes in four different ways. In the `union` statement, two or more shapes are added together. With the `intersection` statement, two or more shapes are combined to make a new shape that consists of the area common to both shapes. The `difference` statement, an initial shape has all subsequent shapes subtracted from it.

And last but not least `merge`, which is like a union where the surfaces inside the union are removed (useful in transparent CSG objects). We will deal with each of these in detail in the next few sections.

CSG objects can be extremely complex. They can be deeply nested. In other words there can be unions of differences or intersections of merges or differences of intersections or even unions of intersections of differences of merges... ad infinitum. CSG objects are (almost always) finite objects and thus respond to auto-bounding and can be transformed like any other POV primitive shape.