A
primitive is a term used in computational
geometry to denote one of several basic
geometric shapes, such as a
cube,
ellipsoid,
sphere or
triangle. When using a
ray tracer, typically many world objects are defined in terms of simple primitives, for which
ray-object intersection formulas are easy to derive and implement in software. Other interesting shapes can often be described through a
constructive solid geometry (
CSG) approach to combining primitives.