If a transparent union is used those surface will get visible. The merge operations can be used to avoid this problem. It works just like union but it eliminates the inner surfaces like shown in the figure below. Merge removes inner surfaces. The last object covered is the light source.
Light sources have no visible shape of their own.
They are just points or areas which emit light. The different types of light sources and the optional modifiers are described in the following sections. Section 7.5.6.1 Point Lights A point light source sends light of the specified color uniformly in all directions. Its location is described by the location keyword and its color is given by the color keyword. The other keywords will be explained later.