Shadow mapping is a popular method of rendering shadows for a three-dimensional scene. There are two popular ways to approach omnidirectional light: one is cube mapping and the other is dual-paraboloid mapping. This chapter presents a new shadow mapping technique for omnidirectional lights using tetrahedron mapping. It summarises the procedure code for generating a tetrahedron shadow map. There are some optimizations to do to improve tetrahedron mapping. One is using a stencil buffer to improve the quality of the tetrahedron shadow map. Another way to optimize is using frustum culling when generating a tetrahedron shadow map for each face. Tetrahedron mapping can be used not only on shadow maps but also on environment maps. Prior to the development of tetrahedron mapping, one had to create an extra cube texture or one more two-dimensional texture for an omnidirectional shadow map.