Scattering Boundary

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will scatter rays according to Lambert’s cosine law. That is, the probability of a ray propagating in a given direction within a solid angle dω is given by cos θ dω, where θ is the angle between the direction of the ray and the wall normal.

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will cause the surface normal to be perturbed by a random angle sampled from a Rayleigh distribution based on the value or expression for the σ (SI unit: rad). The default is 1 mrad.

Rays can be released from a in both reflection and transmission. That is, the options for which include (the default), , or .

If both reflected and transmitted rays are chosen, then, unless total internal reflections occurs, the primary rays are expected to be transmitted.

This section is available when the distribution of released rays is either , or . If activated the wavelength or frequency of a ray can be reset as it interacts with the selected boundaries. The new wavelength or frequency distribution function can be:

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– the wavelength or frequency distribution will follow a normal (Gaussian) distribution with a user defined or μ, and a or σ.

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– the wavelength or frequency distribution will follow a log normal (Gaussian) distribution with a user defined or μ, and a or σ.

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– the wavelength or frequency will be drawn from interval specified by the λ0,min or νmin and the λ0,max or νmax.

See Wall for information on the section .

All of the scattering models (and wavelength or frequency reinitialization) generate random numbers. The option to enter an i (dimensionless, default 1) is possible if in the section for the Geometrical Optics interface, the setting is set to . The section is also shown if the check box is selected under the physics interface section. Select the check box to set the optical path length to 0 when a ray interacts with a scattering boundary.