I'm trying to make use of the point Alpha value and have it drive the opacity of a material. I'm using standard materials, mostly the Basic Surface material. When I set the point alpha to 0, and render it mostly looks transparent with the default MPlay gamma of 1, but if you bring up the gamma you can start to see a ghosted shape of the object. Is this to be expected? Is there a way to really make completely transparent, or am I misunderstanding something?
What I want to do is gradually fade the object in from completely transparent, and, starting from the rear, progressively becoming more and more opaque.

Looking more closely, the issue seems to be that the diffuse colors are being affected by the Alpha value, but the Specular colors aren't. Does that mean that to get the effect I want I'll need to write a custom shader, something that's a variation on the Basic Surface? See the attachment for what I'm referring to.

Despite it's name, the expected scenario is that one is using Alpha to represent the Transparency and not the Matte Transparency.

If you want to use your Alpha attribute to represent the alpha channel of your object, and not just transparency you'll need to remap some stuff in the shaders, yes so that the alpha is going into the alpha of the shader, and not the opacity. You would then likely want to remove it's connection so that it does not multiply against the diffuse color.

Thanks, that was actually relatively easy to do!