Many important optical systems cannot be well described by the sequential ray trace model, such as roof and other prism types, light pipes, or imbedded objects (such as a small bubble of gas inside a glass element).

ZEMAX uses a fully three-dimensional object model for non-sequential components. You can trace rays through a wide range of pre-defined objects (like lenses, prisms etc), objects defined by polygonal meshes and even objects imported from CAD systems using the STL standard.

These components generally require a non-sequential ray trace, where the ray may strike any object in any order, and the ray may even strike the same object multiple times.

When performing non-sequential ray tracing, ZEMAX uses 3D solid models of optical components, and can trace rays through a wide range of solid shapes and faceted components.

Sequential and non-sequential systems

ZEMAX supports both sequential and non-sequential ray tracing in the same lens, if desired. Sequential surfaces may be mixed with non-sequential objects of arbitrary shape, orientation, or position. The ability to handle both types of optical systems within a simple, consistent interface makes ZEMAX the ideal tool for virtually any optical design problem.

One key advantage ZEMAX has over other lens design software is the 3D solid object model for all non-sequential components. Older codes support only non-sequential "surfaces". Surfaces are totally inadequate for defining Fresnel lenses and reflectors, prisms, arbitrary light pipes, etc... ZEMAX offers the best of both worlds: the fastest ray tracing in sequential paths; arbitrary 3D solids in non-sequential groups, and the ability to combine the two in any optical system.

This ability to handle both types of optical systems within a  simple, consistent interface makes ZEMAX the ideal tool for virtually any optical design problerm.