Transparency in HUDs

I want to create labeled buttons in a HUD, but don't want to deal with creating and then paying to import new textures for each label (or each time I want to change a label.) so instead, I use XyText to make my labels. Then, to give my buttons color and shape, I put translucent prims over the labels. That is, the XyText prim lies flat on the surface of the rectangular prim holding my entire HUD and the translucent button prim sits on top of it - think of the buttons on big NASA computers in the 60's .

Anyway, the problem I have is that while this looks just fine normally, when I attach it as a HUD, the transparency works in some places and fails in others, with no consistency. This is illustrated in this screen shot:

http://img162.imageshack.us/img162/7516/hudtransparencyhp5.png

To the left in the screenshot, you see the HUD I have created and on the right, you can see what it looks like when attached. The transparent prim over "Point" and "Create" remains transparent (well, 50% transparent), but none of the other prims (which are set to the same transparency) work. I am completely baffled by this, anyone have any ideas?

Basically, this is the same problem on a HUD, as you see on non-HUD objects with multiple alpha textures in the same line of sight. I believe this is a common problem in 3D graphics, where the render engine doesn't know which texture to render in front of the other. Here's a few links from wikipedia.org which sorta explain it, but a little too technical for me.

Z-fighting
Z-buffering

In your case, both the ZyText alphabet textures and the transparent prim are fighting to be drawn in front of each other.

I recommend making your XYZ text "opaque" and make a single translucent overlay texture, with all the button shapes "shading" over the text. You may have to sacrifice a bit of your design.. but the end result will be more reliable..

Also, can I suggest using llSetText? You'd be surprised how well "floating text" can be used on a HUD. You'll have to make some "host prims" for the floating text.. but you'll be suprised at how consistent and legible the results can be if you plan for it.

hover text on buttons has it's downsides in huds as well.
even once you get it all aligned properly, if an end user doensn't run full screen or a maximized window, the hud objects get shrunk, while the hover text remains at i's original aspect and misaligns and overflows off buttons
XyText is the only true way to offer HUD text that works at all resolutions and display settings. that is till LL gives a functions to grab the clients screen size and allply a scalle to HUD objects accordingly

as far as XyText transparencies and background transparencies, i've had uck moving them further out from the background prim, since it's worn as a hud,the wearer will never see that gap between prims and it will not affect function. that, or, make a XyText texture without the alpha. if you need one, just IM me in world, i have several fonts, all in 3 types, black letters on white, white letters on black, and white on trans. these gave me the best mix of background/font color options. another note. if you make your own on a solid background, you also get to skip all the work to remove the "halo" effect from making it an alpha. =)