Alpha inside the character folder

I am still learning about alpha and alpha highlights and I am totally clueless.
I was looking around in the Second Life program folder the character folder and noticed other folders too.
I open the alpha folders and boy these black and white images look strange.
Example the shirt sleeve looking at in alpha folder I would not have known that is what it is.
Also I like to understand what I am looking at as far as those alpha and alpha highlights
Does anyone have good online tutorial explaining what is secondlife folders and if any of these folders can be modified for artistic purposes within out own games without causing problems?
Example what the possible modifications I could do safely within the character alpha folders?
Could I change how the pant legs are in sliders?
How do I get new textures to recognize the sliders options? Is there something within character or skin folder that I need to copy?

The images in the character folder are all the elements that comprise the default LL skins and some elements used in clothing that control length settings. The appearance sliders alter their tint and the way they're composited together. Once you exit appearance mode, the slider settings determine the recipe used to bake three textures (head, upper, and lower body) which are then uploaded from your client to the asset server and then to anyone who sees you. Things like the sleave alpha are masks that limit things to a specific part of the texture, so for example as you adjust the sleave length (which I think is just controlling a horizontal wipe effect), the sleave alpha mask limits that wipe effect to just the area of the arm. You can alter any of those image files and it will change the way your default skins or certain clothing settings look.You'll want to backup the originals before you experiment with changing those images. You'll also want to backup any altered version you do because they'll end up overwritten the next time you install a new version of SL.

Thanks Chip for responding.
I am feeling bit clueless.
I am just trying to understand how the image I see in character folder for example the shirt sleeve alpha in my own mind becomes what it is in the game.
I just don't get the lines. Or the black images that have white dots that are called highlight alphas

FD, you'll find that if you take those highlight files and overlay them on the clothing/skin templates, it becomes apparent what they're for. On the upper body one, for example, you'll see that white areas mark things such as the tops of the collar bones, tops of shoulders, a little bit of ribbing, things like that. In my opinion they're really not very well done, but their purpose is to add some lighting effects to the texturing, to make the avatar mesh look more detailed than it actually is.

For many of the images in the character folder, you're seeing examples of what alphas can be used for besides just transparency. On the bump maps, for example, the levels of gray from black to white represent not transparency, but altitude. White is maximum height, black is minimum height, and gray is in between.

It so happens that in the TGA files we create for texturing in SL, the alpha channel is dedicated to govern transparency, so that's the only reference we tend to give it in our regular discussions here, but strictly speaking, alpha data could mean anything. An alpha map is just a tool that arranges mathematical values into a graphical sequence. Those values can be used to calculate literally anything you want, from transparency to bumpiness ,to reflectivity, to illumination, to shading, to your personal income tax (and no, I'm not kidding about that last part; you really can do anything you want; math is math is math).

If you want to understand the math, it's really quite simple. Black = 0, white = 255, and for every number from 1 to 254, there's a specific shade of gray. That gives you 256 possible values for each variable, and the number of variables you have equals the number of pixels in the image. Each pixel directly represents one variable.

Once you've got all the variables and values laid out (mapped), whatever calculations are done with that data are the providence of the specific application using the file (which is why Photoshop doesn't automatically show you transparency in TGA files, by the way; since the alpha data could mean anything under the sun, PS has no way of knowing that SL will interpret it as transparency, not that PS even knows SL exists in the first place).

For those highlight files, SL is set up to use the alpha data to calculate lighting information. For the bump map files, it's set up to use it to calculate the height and depth of bumps on the avatar. For the clothing length files, it's set up to use the data in conjunction with the slider settings (more mathematical variables) to determine how to draw the imagery of garments.

Does that help?

Thanks for responding. I am still feeling clueless but I re-read this maybe I get it later.
right now i am just having issue with finding tga files i create in ps for some reason they are going poof.
Why I started looking in this folder was because a friend mention that section.
This is what I am doing but I don't really know how to do it.
Perhaps someone can give me pointers that I can understand.
I am trying to create textures that will work with sliders.
One thing I have noticed is when for example I create new skin tone for slider it doesn't always work with the slider images. Literally nothing really happens or very few things happen.
My friend mentioned the character folder but didn't really go much further then that in how I do use this to with skin tones textures that I am creating.
Any suggestions at this point I don't really know enough about how to use adobe to do layers or how to create the faces I want but when I get sliders to work to recognize skin tones or textures of items I have uploaded I make pretty good shapes and clothes.
I can do more with photoshoppro because I am use to the program yet I do run into issues with things like alphas and layers because I just don't understand them.
Anyone have suggestions for real beginner explaination of layers and how to use alphas,etc? I have adobe 6 and creative suite 1 its new program for me I don't entirely get it and Paintshoppro 9 which I know little bit better except when it comes to mask and layers.
P.S.
I have noticed certain textured images snapshots I edit be it with psp or adobe don't always turn out the way I want they either are squished or something else is bit off about them. Or they aren't able to recognize certain slider controls. By the way.

For what it's worth, you can take a look at this makeover kit I made quite a while ago. It uses many of the client side alphas found in the character folder related to skin texturing. If nothing, it will allow you to manipulate and experiment around with many of the alpha textures in Photoshop without changing any of the current textures in your own character folder. The kit does not get into the bump maps or clothing slider limits, so you are on your own with those.

What program do I need to open ATTN files? I tried to view it but it doesn't open with my version of Photoshop, Creative Suite nor Photoshoppro.
I think I previously had this file from my browsing the forum boy does the appearance to slider tattoo conversion look differently with Adobe compared to Photoshoppro.

FD, those sound like Photoshop action files. To play one, drag it into an open image file, go to your actions palette, and press Play.

I created the kit with Photoshop 7.01. The PSD file should be compatible with most versions of Photoshop after 5.0. The *.atn file is not neccessary to work with the kit, and may not be compatible with all versions of Photoshop after 7.01. It simply generates alpha channels in the proper location.

Hey Choosen,
Do I need specific file or can I just use any textured image?
I just open Adobe and I color tablet and dragged the ATTN file from the slider kit it let me do it but it didn't show me anything nor look differnt.
I think I am missing something.
Edit: I looked in layer history and I see it not exactly sure what to do with but its in folder noticed also there is other sections light etc
I think I need to find book to understand this all. LOL