saved textures lose alpha in Photoshop

I have the following problem: I'm saving textures with alpha parts from SL to my HD as .tga - but when I open them in Photoshop (Elements 7, CS2), all the alpha parts are turned into white. Just re-uploading the saved textures shows them as totally fine.

Does anybody have a solution for that problem?

Thanks in advance
Danny

That's perfectly normal behavior. Take a look at the channels palette. The alpha channel will be there, with the transparency map perfectly intact.

The reason the background appears white is because there's no such thing as layer transparency in a TGA. Any areas that are visually transparent in the working document will turn white the instant the image is saved to the TGA format. As far as the TGA is concerned, those areas are simply blank, and blank means white. The only elements that exist in TGA are color, plus alpha. That's it. Layers don't exist in TGA, and neither does layer transparency.

Further, in no way does alpha automatically mean transparency, in and of itself. An alpha channel is simply a map of SOMETHING other than color. Transparency just happens to be what we use it for in SL. In other programs, it's used for all kinds of things.

Photoshop will never make any guesses as to what you want any particular alpha channel to be for. If PS were to just blanketly say, "Hey, that's an alpha channel. Let's go transparent now," that would severely limit your ability to use alpha channels for anything else. PS is far too good of a program to box you into any corners like that. It waits for you to tell it specifically what to do. You're in charge, not the program.


By the way, to give you an idea of another use for the alpha channel in a TGA, another virtual world platform that I'm currently developing content for (can't say which one, since it's not open to the public yet, sorry) gives you a choice of using alpha for either transparency or specularity on each surface. Using it as a spec map is really convenient for certain things. For example, last night I had to make an assortment of bead-covered shoes. In the color channels, I simply painted the basic patterns of color. Then I just threw a simple noise map in the alpha channel, and presto, instant beads. Mmm, sparkly.

Now, imagine if PS were to force transparency into the image as soon as I add in the alpha channel, even though it's supposed to be a spec map, not a transparency map. I'd have no way of seeing what the hell I'm doing. All that noise would reduce my image to looking like scattered grains of sand on a checkerboard. It would be a disaster. By NOT making such assumptions, PS allows me to do my job.



Incidentally, the presence of that white background is often the result of sloppiness, laziness, or simple ignorance on the part of the artist who created the original image. Don't follow that person's example. For best results, always solidify your colors after creating your alpha channel (or before, depending on your preferred methodology). If you don't solidify the background to match the coloring of the imagery, the save-to-TGA process is just going to solidify it to white anyway. Either way, it's solid, since as I said, there's no such thing as layer transparency in a TGA. But by bleeding the colors, you ensure there are no halos in the final texture. Skip that step, and you take a risk.

Thank you, problem solved