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 a 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 creators eye!

Part One: Skin Layers & Alpha Mode: None
You may have heard the general wisdom that Skin textures should always be created using .TGAs.
The reason for this is fairly simple.. .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 fix for this glitch here)

If you’re using an Omega Skin Applier (that is not a relay…) you should never run into this glitch.  All Omega Skin appliers force the skin layers to Alpha Mode: None. However if you see any of the following, you may have an issue:

Symptoms of Having the Wrong Alpha Mode on your Skin Layer:
  • Disappearing Skin layer
  • Disappearing Clothing Layers
  • Glitched skin layer (see image bellow)

 

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.

Part Two: Clothing Layers and Alpha Mode: Blending/Masking
 
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 however:

 

Now, 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 threashold 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 someones crotch! xD)

 

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

Saddly, 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.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?


So how do you Change your Clothing Layer Alpha Modes?

Again, this depends on your mesh…

Tactic A: Check the hud that comes with your mesh. Most recent mesh makers are building the options right in the hud.

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 –> 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 go 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!

Update:

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.