This article explains how to write a DLL for a user-defined scattering function. An example of a Gaussian X-Y probability function is given.

ZEMAX has two features that improve scattering efficiency: Scatter To and Importance Sampling. In this article we discuss the details of each and perform a stray light analysis using importance sampling.

This article explains

• What Sobol sampling is,
• What its benefits are over random ray-generation methods
• What its limitations are

This article is also available in Japanese.

This article explains:

• What "simple splitting" is
• When to use it

This article explains how measured BSDF data may be used to define the scattering properties of a surface. An example using BSDF data measured by the Imaging Sphere for Scatter and Appearance, which has been developed by Radiant Imaging, is provided.

This article describes the BSDF Data Interchange file format, as developed by Radiant Imaging, Inc. This file format is required for the user-defined scattering function RI_BSDF.DLL, which is used to apply a scattering distribution as provided by tabular BSDF data on a non-sequential surface.

This article illustrates use of the Rayleigh distribution to model bulk scattering.

This article describes how to create sources of any geometrical size and shape.  The Source Object provides the flexibility to convert any object into a source, including any imported CAD object.

This article illustrates use of the Henyey-Greenstein distribution to model bulk scattering.

User-defined objects, scatter functions, sources etc are dll programs that communicate with ZEMAX. In this article I show how to write such programs in Fortran. Sample code is provided.