You can set the 'blend' property of a shader, to make the
whole shader transparent.
Alternatively you can set the blendFunction and blendConstant
of an individual texture layer within a shader.
A third method would be to use a texture image which contains
an alpha channel. For this, ensure the textureRenderFormat is set
to #rgba8888 so that you have 8 bits for the alpha channel (rather
than the default 1 bit).
For more info look up all these in the director help: Shader
-> properties, blendFunction, blendConstant,