creating Alpha in Gimp for Unity

Unity Engine
1

Hi friends,

i’m a bit despaired about creating alpha in gimp(shop) … i’m forced to do so because i cannot afford buying PS.
What i would like to do is creating a a texture with has an alpha channel which can be used by unity,
for example for the specular shader, to have more control over the gloss, as well as for transparent textures which are not only coloured in grayscales (to let unity build this alpha channel for me).

so i`ve messed around with gimpshop quite a lot now, but i still don’t get it.

There are two kinds of results:
First kind is: i create a picture with an alpha channel, and make some areas more alpha than others … gimp itself tells me there is an alpha channel, and its also visible because i can see this little light-grey and dark-grey cubes which gimp paints to make that visible.

When i export that to .psd-format, and import it into unity, unity doesn’t read this alpha channel … i have a texture with a hole in the middle then, and moving around the slider in the transparent/cutout-shader proves me that it indeed hasn’t got an alpha channel yet.

In the tutorial there was some photoshop file which one has to import to use this special alpha … but gimp cannot handle this file.

My question may be too much, but i would be very happy if someone could write me a simple step-by-step tutorial on how to make a simple alphachannel in the shape of a cube which overlays a texture, which would then work inside unity while the texture keeps its look.
(so that if i have a red texture, i don’t get a grey shade over it where the new alpha information is set)

Perhaps i have a fundamental misunderstanding of this stuff, but i imagine this kind of alpha information as a seperate one dimensional channel, into which i could ‘paint’ shapes.
The tutorials i found all did the same: they created alpha information which was considered alpha in gimp, but not in unity, and additionally changed my main texture which i !don’t! want to happen.

Really hoping that someone can help me here because i have tried a lot and still not getting results at all.

2

I think GIMP is not 100% friendly to psd files especially when it comes to alphas (I have tried importing psd files into GIMP and it messes aplha channels quite often).

Just save your file into png and it will work.

3

thank you very much for that info (at the time i’ve no time to work on unity, but i’ll for sure try that out and tell you how it worked, that’s some idea i for myself would never have i quess =))

4

I’m using gimp too but if something is transparent, how could I bring it into unity and still be transparent? .png can’t do transparent. Is there another way?

5

.png can do transparent just fine.

6

Make sure you fix the problem that occurs at the edges of a transparent picture when displayed in Unity.

The PNG export in GIMP has an option to save underlying color data in transparent areas, and make sure you do add proper color in the edges of transparent objects. I usually just add an alpha mask and color beyond the opaque areas to achieve that.

7

TGA is another option if PNG isn’t working out for you.

8

simple:
http://www.youtube.com/watch?v=pGPJhT5lUpE