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.