A value of 0 or 1 is fine for almost all raytraces. Raytracing time increases dramatically for each increase in this parameter. Raytrace Effects Surface Width Surface Width is only used for transparent objects with the raytracer. This parameter simulates the thickness of transparent objects that are made of single surfaces. Results will not be identical to building objects with thickness, but good results can be easily achieved where it may be difficult to build the thickness of a surface.
Thickness is defined in world units.
This effect works best where the edges of the glass are not visible, such as closed surfaces, or shapes such as car windshield. Shade is used to vary the transparency across a surface with respect to RayTracer shadows. It is an effect that makes shadows of transparent objects brighter in the center, simulating the focusing of light. The valid slider range is from 0 to 1, where the default value of 0 produces shadows of constant intensity. Depth controls the distance a ray will travel beyond a transparent surface.