I've muddled through using Gimp for about a year now but I'd really like to
understand alpha layers better now. I have a few questions but maybe a
referral to a good resource will help me clear this up. The online
manuals
haven't clarified this for me and I'm getting a strong desire for some
detailed understanding:
I use Gimp to make textures for user generated game maps for Unreal
Tournament. Much fun and a creative outlet. A great many of the tools
for
materials utilize only the alpha channel of a texture (image - default
input
format is targa). Eg. opacity, self illumination, bump map, specularity
map
etc etc, all are derived from seperate alpha layers (uses grayscale 8 bit
only) while the rest of the texture is ignored for that shader function.
So
if you want all these things to use different alpha layers then you save a
different texture for each. Fine except that I'm having a tough time
getting into and out of the alpha layer.
What I'd really like to do in the end is to be able to take an RGB image,
desaturate it and then manipulate the gray scale image in GIMP, save that
as
the alpha layer back into the original RGB image for ex****t to Unreal.
But
it doesn't seem to be that simple!
For example what is the difference between a transparancy mask and an
alpha
layer? How can I start with a quick mask and then edit that into an alpha
layer? When I add alpha layer in the layer menu, often nothing seems to
happen!
Once I have an alpha layer, sometimes a monkey banging on the keys can get
it to have a green border in the layer menu and then I seem to be able to
edit it, but I can't seem to consistantly get to that green border around
the thumbnail image. After a while, the monkey seems to also be able to
make the alpha layer border red, and then it doesn't seem to influence the
image. How does one go back and forth?
What happens with multiple layers - can they each have a different alpha
channel/ layer? (that would be nice) Do the effect of each layers' alpha
channel interact up the layer stack or are they only active on that
particular layer? Can you make a "master" alpha layer (at the top/ bottom
of the layer stack???) that will have ultimate control over the final
alpha
of the image but still leave the layer structure intact or do you have to
compress the image first?
Thanks for your input
Lyle
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