Impact of drawing resolution on ray tracing

Most of the time, the default drawing resolution of native objects in a non-sequential system is enough for providing a good “first guess” as to the location of the ray-object intercept points to be used during ray-tracing. However, there may be cases when a ray misses an object it was meant to hit. This is a rare phenomena that typically only affects rays incident to steeply curved objects, but when it occurs, increasing the drawing resolution will ensure that the ray strikes the object.

Authored By Alessandra Croce


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In OpticStudio's Non-Sequential Mode, the drawing resolution setting is used to generate a "boundary region" around each object. If a ray does not cross the boundary, then the program assumes that the ray will not hit the object. In some cases, this means that a ray might miss an object it was supposed to hit when the resolution is set too low.

Drawing resolution settings are only applicable to the layout plots. This setting affects how objects are rendered and provides a "first guess" as to the location of the ray-object intercept point. For a ray trace, the accuracy is not limited to the drawing resolution settings so long as the drawing resolution is sufficient to provide an adequate first guess. 

A simple example

In the attached file you will see an example of the impact of the drawing resolution on ray tracing.

A system formed of a Source Gaussian, a Torus Surface and a Detector Rectangle has been replicated four times. In each system the source is located close to one end of the Torus Surface, so that all rays generated by the source are entering the pipe defined by the torus surface. Note that the material of the Torus Surface is "MIRROR", hence all rays entering the pipe should bounce on its surface, and hit the detector located at the end of the pipe.

For comparison, all 4 systems are identical except for the drawing resolution of the Torus Surface. This has been defined differently in the Draw properties of each Torus surface, and has been consequently reported in the Comment column of the Non-Sequential Component Editor:

You will notice that the 3D Layout shows that some rays are escaping the pipe, and that the higher the torus surface resolution, the fewer rays are escaping.

In order to show that this is not just related to the drawing rendering, launch a ray-trace. You will notice that in this case there are no ray errors in the Ray Trace Control:

However if you compare the results of the ray trace for the four systems, you will notice that the higher the torus surface resolution, the higher the total hits on the detectors. Yet, according to the ray trace above, no rays should be lost. Here we see that only the detector with the customized drawing resolution will collect all the rays generated from the corresponding source:

Comparing the results of the four systems clearly shows the impact of the drawing resolution of the torus surface on ray-tracing: if the drawing resolution is not sufficient to provide an adequate first guess, the ray-trace shows results which are inaccurate and inconsistent with our expectations.

Note: This behaviour will strongly depend on your system and there is no general advice for when the drawing resolution needs to be increased. Moreover, OpticStudio does not have means to detect such a potential issue, therefore no ray trace errors will be generated in this case. It is up to the user to inspect the results (e.g. via the system layout) to ensure accuracy.


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