Reference:Intersection

The intersection object creates a shape containing only those areas where all components overlap. A point is part of an intersection if it is inside both objects, A and B, as show in the figure below.

The intersection of two objects.

The syntax is:

INTERSECTION:
  intersection {
    SOLID_OBJECTS...
    [OBJECT_MODIFIERS...]
    }

The component objects must have well defined inside/outside properties. Patch objects are not allowed.

Note: If all components do not overlap, the intersection object disappears.

Here is an example that overlaps:

intersection {
  box { <-1.5, -1, -1>, <0.5, 1, 1> }
  cylinder { <0.5, 0, -1>, <0.5, 0, 1>, 1 }
  }