In Mantid we use constructive solid geometry (CSG) to describe the shape of an object. This involves the creation of more complex shapes by the union, complement or intersection of simple primitive surfaces.
Defining our object shape using CSG was selected for a number of reasons:
Mantid has direct support for creating various shapes directly, including
Some of these shapes are infinite surfaces (the infinite plane, cone and cylinder) these are therefore not very useful on there own, but in combination with other shapes they can be capped as required.
For example if you cap and infinite Cylinder with two infinite planes you get a finite capped cylinder. This is in fact how the Cylinder shape is defined internally within Mantid.
For more on this see HowToDefineGeometricShape.
Category: Concepts