Ray Tracing
The Ray Tracing () study and study step are used to compute the trajectories of rays. The Ray Tracing study step is a special case of the Time Dependent study step. The time steps taken by the solver can either be specified directly or by specifying a set of path lengths and a characteristic group velocity. Built-in stop conditions can be used to stop the solver when no active rays remain, or when the intensity of active rays is negligibly small. Except for the section below, see Time Dependent for all settings. This study requires the Ray Optics Module or the Acoustics Module.
For example, this study is used with the Geometrical Optics or Ray Acoustics interfaces to compute ray trajectories. By specifying the range of time steps in terms of the maximum path length, it is possible to deduce the optimal study settings from the geometry size and ray properties.
Study Settings
Select a Time step specification: Specify time steps (the default) or Specify maximum path length.
•
If Specify time steps is selected, select a Time unit from the list (the default is ns) to use a convenient time unit for the time span of the simulation. Then, in the Times field, specify the time interval for the output from the simulation using the selected time unit.
•
If Specify maximum path length is selected, select a Length unit from the list (the default is m). Then specify a list of Lengths using the selected unit. Enter a Characteristic group velocity (SI unit: m/s). The default is c_const, the speed of light in a vacuum. The time steps taken by the solver are computed by dividing the list of lengths in the Lengths field by the characteristic group velocity.
From the Tolerance list, choose Physics controlled (the default) to use the tolerance suggested by the physics. Choose User controlled to override the suggested relative tolerance with a value that you enter in the Relative tolerance check field. The tolerance settings control the internal time steps taken by the solver, so selecting large time steps for the output times does not affect the accuracy in the time stepping.
Select a Stop condition: None (the default), No active rays remaining, or Active rays have intensity below threshold. If No active rays remaining is selected, the solver terminates immediately when all rays are stuck, frozen, or have disappeared.
If Active rays have intensity below threshold is selected, enter a Threshold ray intensity (the default is 1[W/m^2]). The solver terminates immediately when all rays are either stuck, frozen, have disappeared, or have intensity less than the threshold. This setting can only be used if the Intensity Computation setting for the Geometrical Optics interface is set to Using principal curvatures under Ray Properties.