This options generates a light map, by default the viewer starts with no light map.
To generate a light map choose the angle X and Y of light source and the opacity (0-100).
Angles just take effect when you "apply angles", opacity takes immediately effect on value change.
The light source vector starts as (0,0,-1) meaning all light rays are perpendicular to the map, changing
X and Y angles rotates the light source vector on plane X and Y.
When switching to 3D mode, a small box will appear in the image map just position the box in the area to be generated as 3D, when ready just
click on left mouse button to start the 3D generation.