From: Aleri Darkes
after i create my design i am suppose to merge all (flatten) layers however when i try to do that the option is gray and not selectable. Im not sure if my instructions are missing a step?
Never flatten. There's simply no need for it. It's destructive to your archival workflow, and it yields absolutely zero benefits. Keep your layered work preserved, always. Produce your image using as many layers as you need, save your work (as a layered PSD), and then export to TGA for upload to SL.
I know, there are a few tutorials out there that tell you to flatten your work before you save to TGA, but once again, trust me, it's not something you should be doing. I've been a texture artist for a long time, and with all due respect to the authors of those particular tutorials, I've never been able to understand why they thought flattening was a good idea. It isn't. I'll explain.
First, since TGA is an inherently flat format, the exported TGA will be exactly the same whether the source document was flattened or not, making the flattening step a waste of time at best. Second the only thing the flattening actually does accomplish is to make it MUCH harder to go back and make changes to the source document later if you need to.
Imagine, for example, putting text on a T-shirt, and then discovering a typo after you've finished and uploaded it to SL. If you didn't keep your layers, you'll have to re-create the entire shirt over again from scratch. If you did preserve your layered document though, then all you have to do is edit the one text layer, and then re-export the TGA, a 5-second task at most.
For a more extreme example, it's not uncommon that the PSD files for complex textures (like high quality skins) contain literally hundreds of layers. That kind of thing takes dozens of hours to produce. Could you imagine having to do all that over again every time you want to make a minor change?
That would obviously be redicuolous, but that's what you'd have to do if you'd flattened the file. So again, never do that. Keep your layered PSD intact at all times, and save to TGA whenever you're finished. That way it's easy to go back and make any changes you need at any time.
By the way, depending on what version of the software you're using, when you export a layered image to TGA, it may prompt you that the TGA will be saved as a copy. This is perfectly normal, nothing to be concerned about. The prompt can look like a warning, which is easy to misinterpret as something being wrong, but all it really is is just just a confirmation that your layered work will not be overwritten by the TGA export. Some versions of PSP and Photoshop give you that confirmation upon saving; some don't. It's no big deal either way.