Possible Alpha Layer Problems

Part of the thing with mesh clothes is alpha layers. Even with prim and sculpty shoes and other attachments alpha layers have become a part of wearing these items. Invisaprims are a thing of the past. There is a thing in Second Life™ Alpha Masks that has been over looked by many. It may come back to bite us if we don’t pay attention… or not.

Alpha Mask Edit Panel

Alpha Mask Edit Panel


We call them Alpha Layers and they do layer, but, they do NOT layer with clothes. The real name is Alpha Mask. The Alpha Mask has its own channel. That makes sense to you if use channels in Photoshop. If not, just understand that a channel effects everything associated with an image, like all the layers.

You can layer clothes and skin as they are in a texture channel. You can stack textures in a clothing channel like SHIRT. But the clothing layers are a bit like folders in the texture channel. You can’t change the order of the folders; Jacket – which is on top of: Shirt – which is on top of: Undershirt – which is on top of Skin stay in that order. You can add shirts and rearrange their order.

The Alpha Mask is a channel that affects all the clothes layers; Skin, Shirt, etc. We can add masks together. We can think of that as layering, but it is really more like ADDING transparency.

Check out the SL Wiki on Alpha Masks to get the limits. I can put on 5 Alpha Masks, which may be why many of us think of them as layers. But, they don’t work the same.

In clothing layers the top layer covers the layers below. Put on a blue shirt and then a red shirt and you will appear to be wearing a red shirt.

Alpha Masks add together. If any part of any Alpha Mask is white then the corresponding part of the avatar is transparent.  The order of the Alpha Masks does not matter.


You may notice that there are check boxes in the Alpha Mask Editing panel. If you check that box the entire part of the avatar it covers becomes transparent. Some designers use a transparent texture rather than check the box. It makes a difference which you do.

Using the Checkbox takes that part of the avatar out of the avatar bake process. It is more efficient, but right now you can’t see any difference between using a clear texture and the checkbox. Well… I can’t. That will probably change with the roll out of Server Side Avatar Baking. (Due in late February, if things go well.)

The idea is the server side baking will be as much like viewer side baking as possible. The hope is most users, like 99.9%, won’t notice a visual difference in the result. But, the Lindens are NOT guaranteeing that clear textures are going to mask as well as using the checkbox. They are warning users to make use of the checkbox where appropriate to avoid possible problems.

At this point we can’t tell how much of a problem it will or won’t be. One can only check it out via the Sunshine Project Viewer and the supporting server code, which can be found in ADITI. See: Project Sunshine-Server Side Appearance.

Take Away

If you are using solid white square Alpha Masks to hide the entire avatar, stop. Use the Alpha Mask Editing checkboxes.

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