Because the 3D cursor samples the pixels of the screen, on Looking Glass 32" systems it can have an adverse effect on performance.
The 3D Cursor is a special component designed to make it easier to navigate 3D scenes on the Looking Glass. It works similar to a normal mouse cursor, but adds the ability to sample the 3D scene so the cursor will adapt to your model. This allows you to point out and select objects regardless of what distance they are from the camera. Combined with the orbit controls script this provides a simple way to cleanly navigate a scene.
To try out the 3D Cursor yourself checkout Example 4 in our Unity SDK.
By default, the 3D cursor will scale with the HoloPlay Capture object so that it will always be visible, you can disable this if you'd wish to manually control the size of the cursor.
Enabling UI Cursor mode allows you to use the 3D cursor to interact with a 2D UI. This was mostly used for the Looking Glass Pro systems, and has limited use with current gen Looking Glass systems.