nramco nracmo, (woops!)
Optic segments overflow means that an optic is being broken up into more than 24 individual occluded/unoccluded segments, where you can think of an entire optic depicting a point in 3D space and the length of the optic is broken into "visible" and "invisible" sections. If you have a model of say a triangle way in the background and then a set of 20 vertical rectangles that make parts of it visible and invisible all along the viewing angle then its optic segments will get broken up too much.
Also, it's recommended that you disable 'Intersection Resolution', which can also cause a segment to be chopped up into too many segments. It was more of an experimental feature but I have yet to get it working as good as I was originally hoping, and it's best to leave it disabled.
Your resulting hologram should be 'opaque' as long as 'Occlusion Detection' is enabled. This will prevent optics from being created for back-facing geometry, and also clip sections of optics that are blocked from view by foreground geometry. If you also want it to appear completely opaque in the view you can enable 'Show Faces' in the View menu.
Also, I don't recall if it's mentioned anywhere, but the 'Light' slider controls the expected/assumed azimuth (pitch angle) of the illumination source, where when the slider is at the top-most position the light source is assumed to be directly above the hologram, shining down on it at a 90 degree angle from the direction the hologram is facing. At the bottom of the Light azimuth slider is 60 degrees, so still from somewhat above the hologram but shining more 'head-on'.
The purpose is to accomodate the use of a ceiling light source in different sized rooms, where a larger room with a lower ceiling would use a Light angle that has the slider closer toward the bottom, and a room with a light more directly above the desired hologram position will have the slider up higher.