This brings up the "Transparency type" selection menu for the viewer that has the following controls:
Screen-door
This option uses a fill pattern to simulate transparency effects (fastest, least photo-realistic). The fill pattern may be as simple as turning every alternate pixel off.
Alpha blending
Alpha blending option produces more realistic transparency effects (slow, more realistic). Alpha blending types are as follows, in order of increasing realism, and decreasing speed of display (depending on the type of graphics hardware on your machine):
Additive
Additive blending option adds the transparent object to the colors already in the frame buffer.
Delayed additive
Renders opaque objects first and transparent objects last.
Sorted delayed additive
Draws opaque objects first followed by transparent objects, then sorts the transparent objects by their distance from the camera and draws them from back to front.
Multiplicative
Combines source and destination colors and alpha factor to produce transparency effects.
Delayed multiplicative
Renders opaque objects first and transparent objects last.
Sorted delayed multiplicative
Draws opaque objects first, then transparent. Transparent objects are sorted by their distance from the camera and drawn from back to front.