Understanding Alpha Modes

Understanding Alpha Modes 

If you’ve ever had layers disappear on you, layers that are blacked out, lace that is mutilated or skin layers that disappear at some angles, it’s likely to be because of an improper alpha mode settings!
Luckily, most of these issues are solved with proper scripting, and with a little bit of knowledge, you can fix issues that have been missed by the creator’s eye!

Understanding Skin Layers & Alpha Mode: None

Skin Layers & Alpha Mode: None

You may have heard the general wisdom that Skin textures should always be created using 24bit TGAs.
The reason for this is fairly simple…in SL 24bit TGAs default to Alpha Mode: None.

This is very important because skin layers should ALWAYS be set to Alpha Mode: None. Any other setting will create an array of frustrating glitches,

There is, however, a glitch with 32 Bit TGAs that makes the alpha mode of the skin change when the texture is applied.  Thankfully, there is a way to script against this glitch. (Mesh makers, you can find the bellow)

If you’re using an Omega Skin Applier you should almost never run into this glitch.  All Omega Plug-ins and Listeners force the skin layers to Alpha Mode: None and we make sure the Mesh Makers we have Relays for, understand how to fix this glitch. However, if you see any of the following, you may still have an issue:

Symptoms of Having the Wrong Alpha Mode on your Skin Layer:
  • Disappearing Skin layer
  • Disappearing Clothing Layers
  • Glitched skin layer that you can see halos of itself through (see image to the left)

How to Fix:
This depends heavily on what body you’re using, and with no-mod bodies, you may be out of luck.

Tactic A: Convert the Skin appliers you have into Omega appliers and use them again.  Omega Skin appliers always force the Alpha Mode to None, fixing your issue. This, however, does not work with any mesh that uses a Relay. (Currently Sking, Maitreya, Jiggle Booty, ect)

Tactic B: If your body is mod, you can rez it on the ground and edit it.

  1. Rez the body on the ground.
  2. Rightclick –>
  3. Go to the texture tab.
  4. Use Select face to select the skin layer.
  5. Change the Alpha Mode to None as shown here.
  6. Repeat for every link and face of the skin. (There may be alot of these thanks to alpha-cut huds being so popular)
Tactic C: Open up a fresh copy of the body and try applying the skin again. If it still has the issue, contact the skin maker and ask them to redo your appliers with .tngs.

Fixing the Skin Glitch (For Mesh Makers)

Safeguarding your Mesh against 32 bit Skin Textures
‘borrowed’ with permission from Galathir Darkstone ^.^

If you make a rigged or fitted mesh product that supports skin appliers and clothing layers over the skin, it is likely that at least one of you customers has run into a problem with the ‘skin’ seeming to vanish under the clothing. This is caused by a conflict between the overlapping 32bit textures. This is likely related to the long time alpha sorting issues we’ve seen on prims and un-rigged items for years now. I’ve been trying to get the word out to skin makers that they should use 24bit textures for their appliers… but as you can imagine, getting everyone notified… and then convinced it’s worth the time to redo the appliers is a challenge.

Well there’s good news. Thanks to Server Side Rendering and Materials, you have an option to make sure that 32bit textures are not an issue: Alpha Blending Mode. Now this is something you could set by hand in the Edit window, but testing seems to indicated that applying a 32bit texture -can- change it from your manual setting. So… the best solution is to make sure you set this in your scripting right after you apply the incoming texture. Now that the Parameters are live across the grid, this is simple enough.

This line of code, supplied with your link number and face number, will take care of it:


PRIM_ALPHA_MODE_NONE basically turns off the alpha channel, even if the texture is 32bit. Boom. No more vanishing skin.

Hope this helps.

~Galathir Darkstone
The Architect of Sin
Owner/Creator, Sinful Needs

Want more information about this problem?

Understanding Clothing Layers and Alpha Mode: Blending/Masking

Clothing Layers and Alpha Mode: Blending/Masking
Clothing missing or appearing rearranged on your mesh body? Read on!
Everyone seems to have an opinion on what is better for your clothing layers… Alpha Mode: Blending or Alpha Mode: Masking.
The long and the short of it is this:
Alpha Mode-Blending
Gives you lovely soft Edges as seen here with this lace dress top from Maai:
Alpha Mode-Masking
does this.  Every point on the texture is either “on” or “off”
eliminating all soft transitions from transparent to opaque.
But this isn’t the whole story.  With Alpha Mode-Masking, you have what is called a threshold. The image above is at the commonly used 150. If can, however, be changed, the image on the left is Threshold 0, the middle is 50, the image on the right is threshold 225. (notice how smaller numbers = more coverage?)

So why use alpha mode masking if it looks this terrible?

a)It doesn’t always look this terrible. Alpha Mode Maskings main issue is with sheer, lacy items. Solid items look much better, like the bottom of the same dress…the image on the left is alpha masking, the image on the right is alpha blending. Unlike the lace, there is only small decrease in appearance, especially when viewed at normal distances. (Ie.. your face not up in someone’s crotch! xD)


b)You can’t have more than one layer set to Alpha Blending without having mesh glitches.

Sadly, all graphic cards/viewers/meshs/clothing/textures/ect have this issue. It’s not something anyone can work around. It’s a fundamental flaw in how graphic cards (all graphics cards) handle semi-transparent textures. This is why in video games you rarely see alpha blending. (Go ahead, peek around your favorite video games, you will find they just bake all the textures into one layer 99% of the time, and that when you look closely, those trees and shrubs that look so lush, have the telltale hard edges of Alpha Mode Masking.)

Symptoms of multiple Alpha Blending Layers:

  1. Layers flickering
  2. Layers disappearing or not showing up
  3. Layers appearing, but in the wrong stack order. (ie, bras on top of tops!)

Basically, you need to plan your outfits so only one layer requires alpha blending. This can involve some tough choices… do you want the outermost (and most visible layer) to have it, or the underlying lacy layer?


There seems to be some evidence, that wedging a layer with Masking Mode in between two blending layers will also drastically reduce.. if not eliminate alpha-glitches entirely.  Unfortunately, because of the nature of the problem, it is hard to test this definitively, but keep it in mind if you find yourself needing two layers to have blending.

Changing your Clothes Alpha Modes (For Customers)

So how do you Change your Clothing Layer Alpha Modes?

So you know now you need to change the Alpha Modes on your clothing layers. How?

Tactic A: Check the hud that comes with your mesh. Most recent mesh makers are building the options right in the hud. Look for options such as “Blending”, “Masking”, “Alpha Mode”, “Masking Mode” etc. Ussually, they are found right next to any buttons that let you turn your layers on and off.

Tactic B: If your body is modify, you can rez it on the ground and edit it.
  1. Rez the body on the ground.
  2. Rightclick –> Edit
  3. Go to the texture tab.
  4. Use Select face to select the clothing layer you want to change.
  5. Change the Alpha Mode to Blending or Masking as needed.
  6. If you’re changing the mode to alpha masking, remember to also set the “Mask cutoff” or “threshold” field. A recommended starting point is 150, but you should play with it to see what looks good to you.
  7. Repeat for every link and face of the layer. (There may be alot of these thanks to alpha-cut huds being so popular)
A tip for the adventurous: Nothing says every face of a clothing layer needs to be the same alpha mode and/or threshold. If you have something lacy on calf and on your thigh, and there are alpha cuts between the two, you can set textured parts of each layer to blending,  and set the rest to masking. The important thing is that no two overlapping faces can be alpha blending!

Alpha Modes for Head Creators

As head creators, it’s a bit trickier to handle the Alpha Glitch. Makeup and Tattoos rarely look good in Masking mode, so adding a “Mask” button isn’t very helpful.

There are two basic tactics that I am aware of:

  • Don’t overlap layers. Simply make a full head layer and cut it into zones.
    • Pros:
      • Easy to do. Great for Beginners
      • Zero Glitches.
    • Cons:
      • Some items NEED to overlap. Beards and Hairbases, for example, should overlap at the temple.
      • Eyebrows and eyeshadow tend to overlap slightly as well.
      • Lashes cannot be blending.
  • Do multiple layers, but make them all part of the same prim.  Somehow, this cuts down on glitching dramatically. (I think it’s voodoo). But by making your skin face 0 and adding layers as new faces on top of that, our graphics cards have a much easier time figuring out whats going on.
    • Pros:
      • Almost no Glitches.
      • Have up to 7 overlapping full head layers.
      • Lashes can be blending Mode! (You just treat them like the rest of the layers)
    • Cons:
      • A bit of a bitch to do in Blender if you’re not experienced.
      • If you want more then 7 makeup layers, you’ll need to cut the head into pieces and do some blender jigsaw, ensuring nowhere on the head do alpha textures overlap.

As for the skin. See “Fixing the Skin Glitch (For Mesh Makers)” above.