SL has Alpha Layers for the avatar, which is what we are talking, and Alpha Blending for prims. It takes far less render time for Alpha Layers. But, Alpha Layers can only be 100% transparent or 0% transparent, opaque. Alpha Blends can be any measure of transparent from 0% to 100%. We cannot use blends with the avatar Alpha Layers. With system clothes we can use Alpha Blending. That seems to confuse some people and some tutorials are not clear about where we can do what.

Just remember Alpha Layers are a special thing in Second Life. They either are or are not transparent. Simple.

It may clear it up to think of Alpha Layers and Alpha Maps. Prims and system clothes use ‘Layers’. So, just as we can make a layer in GIMP/PS 50% transparent, so too we can make prim and clothes textures partially transparent.

In the 3D modeling world alpha maps are used for 0% or 100% transparency. Their purpose is to reduce render time when a blend is not needed.

In SL the Lab tried to make the idea of Alpha Maps used on avatars easier to understand and to a degree industry-label compatible. The result is debatable. But, I can’t say I can think of a better way to describe what we have in SL. You may notice in the Appearance Panel the Alpha Layer creation panel is titled Editing Alpha Mask. Mask and map are often used interchangeably in 3D modeling.

In modeling programs we see ‘Materials’ that have transparency. Somewhere in the material making process we can add an alpha mask/map. In SL our avatar alpha masks/maps are part of a clothing layer, which the Lab chose to name Alpha Layer. I think that is consistent with SL naming. But, it is inconsistent with what we know from image editing and 3D modeling, thus confusing.

Limits

We can wear 5 Alpha Layers. Each AL can have 5 alpha maps/masks (images). So, we have lots of room to be creative. Plus it is possible to combine multiple AL’s we want to wear into a single AL. We just need to combine the maps in GIMP/PS.

I almost always have on an Eyelash Remover, my shoes’ AL, and a Slink hand remover AL. That is three of them. If one goes with a Slink head, that is 4 AL’s. So, we are rapidly reaching the limit. I already see Slink combining feet, hands, and head AL’s into a single AL. We can do the same.

Making the AL

To make an Alpha Layer we create an image that tells the system which parts of the avatar to render and which to hide. The details of how to do that vary because there are numerous good ways to accomplish this task.

However we go about it we are going to create an image with opaque and 100% transparent areas.

The video above shows a Blender process. There are others. Check out YouTube.

There is a good example of the GIMP/Photoshop process on the Second Life Designer blog. See: Second Life Alpha Masks: Secrets Revealed! I think this so well done I’m not going to make my own and basically repeat it.

Knowing What to Make Transparent

The making part is pretty straight forward. Knowing what to make transparent is a problem. If we are trying to tweak an existing transparency to come closer to the edge of a clothing item, it can be hard to know how much to change the alpha map.

We may not be able to get the alpha layer map/mask for an item. I see no reason why these textures cannot be Full Perm. One really has to go to some effort to protect them as just making them no-mod doesn’t stop the IP thieves. It seems to me a good selling point would be making those images full perm so customers could export and tweak them.

If we cannot get the original alpha map textures for our item, we can use the clothing templates and start guessing. There are no big secrets or quick solutions. It is trial and error.

If we have the Alpha Layer textures, we can easily tweak them. We can color in more area or clear areas by erasing. We have a good starting place and the trial and error effort is greatly reduced.

Since we likely cannot export the item the Alpha Layer is made for, we are into a trial and error process. We can get our new purchase to the Preview (Beta) Grid by changing our password, waiting 24+ hours, and logging in then we can upload our new alpha map for free and make a new Alpha Layer. We repeatedly try it out, adjust, and import until we have it the way we want.

Once we get it right, we can upload the final Alpha to Second Life, build our Alpha Clothing Layer, and add it to our outfit.

Some Help

With some items you can find where the alpha map limit is. In SL put on the alpha layer. Switch to Wire Frame mode (Ctrl-Shift-R). The part of the mesh hidden by the alpha will not show. You can see where on the avatar mesh the alpha ends.

The clothing templates replicate the mesh layout. And of course in Blender or PS 3D you can see the same mesh. So, you have a bit more precise guide for making a new alpha mask.

The image above shows my avatar with a Slink hand wearing the Slink Alpha Layer. The image is not that great, but there is a double line where the hand mesh over laps the avatar arm mesh. (yellow arrows) The Alpha Layer seems to end on a edge-ring of the arm. Using most any clothing template you should be able to find that EXACT edge-ring and make an alpha mask of your own.

Here I have highlighted the avatar mesh of the leg. I’ve taken off the NCore foot & shoe. The NCore alpha for this shoe hides part of the leg and all foot. We can see that it too ends on an edge-ring. We can find that edge-ring in a clothing template and use it as a guide for making a mask that works with the Slink hands and NCore feet.

Summary

Making Alpha Layers and their component masks is pretty straight forward. I hope this tutorial straightens out some of the terminology and supplies the parts of the process many tutorials simply omit. Because some of us consider these things obvious, because we deal with it so much, we tend to leave things out.

So, let me know if something is still not clear.