Order of Initialization of Auxiliary Dependent Variables
When rays are released, the variables defined for each ray are initialized in a specific order. The initial values of ray variables can only depend on the values of variables that have already been defined. The order of dependent variable initialization is governed by the following rules:
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The initial ray position is always determined first.
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By default, user-defined auxiliary dependent variables (that is, those that are defined by adding an Auxiliary Dependent Variable node to the physics interface) are initialized after all other variables. They can instead be initialized immediately after the ray position vector components by selecting the Initialize before wave vector check box shown in the release feature Initial Value of Auxiliary Dependent Variables section.
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If more than one user-defined auxiliary dependent variable is present, these variables are initialized in the order in which the corresponding Auxiliary Dependent Variable nodes appear in the Model Builder.
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The remaining degrees of freedom are defined in the following order (each listed group is initialized simultaneously, and the variables within a group cannot reliably be initialized in terms of each other):
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Help variable for the perturbation of initial ray direction at illuminated surfaces
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Ray frequency or vacuum wavelength
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The wave vector components, optical path length, and total power transmitted and reflected by gratings
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The integral of the attenuation coefficient along ray paths and the components of the unit vector that indicates the direction corresponding to one of the principal radii of curvature
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The principal radii of curvature, initial principal radii of curvature, intensity, Stokes parameters, and help variables for computing the curvature tensor and intensity
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The total power transmitted by the ray
Items in each bullet point may not be initialized as functions of items in a later bullet point. For example, the initial ray direction vector can depend on the ray frequency, but the initial principal radii of curvature cannot depend on the total power transmitted by the ray.