How do I save a layer mask as an alpha channel

I have a psd file that contains many layers. One of the layers is a window frame, another is a pane of stained glass. The pane of stained glass has a layer mask that provides partial transparency to the glass. How do I save the frame and the glass as a single tga file with the layer mask as its alpha channel?

You're using Photoshop, I assume.

Basically, you need to go to the channels tab (next to the layers tab) and hit the teeny weeny round button with a small arrow on the right.

Then select 'New Channel'. It will add a new one below the RGB channels.

Then copy and paste in whatever masking you need from your layer into this channel.

Totally white in this channel means show, black means transparent, and grey are the inbetweens.

When you're done, save it as a 32-bit TGA. And make sure 'alpha channels' is checked.

Test and look see in the SL texture uploader.

There is a sticky up here called 'Definitive something something' if you enjoy poetry.

Or you can just hold down the Command/ctrl key, and click on the Mask Thumbnail. That will load the Mask as a selection. Hold down shift and click on any other Masks or Layers you want.

Then go to Selection > Save Selection, and choose to save as a New channel. PS will automatically name it Alpha 1. (This is assuming that you don't have any other Alpha channels. If you do, you'll want to Replace them. There can be only one!)

That's it. You're all set.

Save as a 32 bit .tga file, and upload to SL.