Maya 8.0 Tutorial
How to Control Texture Alpha Transparency in Maya
The Transparency channel specifies the object's transparency.
Objects can have a uniform transparency throughout the geometry or in limited areas. By assigning a grayscale map to the transparency channel you can set the opaque sections (Black) and the transparent portions (White).
The transparency option is available with Anisotropic, Blinn, Lambert and Phong shaders.
Open a scene with an object. Right-click the object and choose Assign New Material > Lambert.
The new Lambert shader panel opens in the Attribute Editor. To change the transparency, move the slider.
The color rectangle affects the object's transparency color.
Click the checker-box next to the Transparency slider to assign a grayscale map (White = Transparent, Black = Opaque).
In the Create Render Node, 2D section, choose Normal and click the Bulge icon.
Render your image an note the effect of the transparency map. You can also adjust the Bulge settings. In addition to procedural textures such as Bulge, you can also use grayscale jpg or tif files.