Adjust transparency of material with alpha-textures?


I’ve just started learning Blender, and 3D in general, so I apologize if this is a “stupid” question or if I’m using incorrect terminology.

I’m currently doing a simple animation of a helicopter for one of my colleagues. The helicopter-model was bought (textures included). I’m animating the rotors’ rotation and the helicopter’s movement.

I did quite a lot of testing with motion blur (different rotor rotation speed / motion samples /camera shutter), but was not quite happy with the result. There was textures of spinning rotors included with the model, and since the helicopter always will be flying (no landing or take-off), I started testing with these instead. (Attachment #1) The main rotor is looking good, but I need to do some further tweaking on the tail rotor.

Material Tab:
Transparency: On (Z Transparency)
Alpha: 0.00

The tail rotor’s material is a combination of two .bmp textures, one for color and one for alpha. It renders correctly. (Attachment #2). But I would like to decrease the opacity of the rotor as well, so that it is less visible. How can I accomplish that? I’ve tried adjusting color / alpha influence and DVar, without success. Do I have to manipulate the alpha channel (.bmp) in Photoshop etc., or can I do it in Blender?




If your alpha is black and white, then you will have 100% influence and 0% influence, shade of gray in between are represented as percentages between 0 and 100. One way you could do this is to create a new map with a gray value for the rotors. There are other ways too of course.

Thank you for your help, ajm! Good explanation.


There are other ways too of course.
I would like to know what the other ways are. Because, quite frankly, I don’t think there are any other ways. It is one of the limitations of the Blender material system. Once you use an Alpha as a map, you lose the ability to make any other part of the object transparent. Or to fade it in and out.