Alpha channels


(PlantPerson) #1

How do I use alpha channels?


(Piraniac) #2

Hi,
Only tga images support alpha channels, so make sure its one of they (i’m assuming ya know how to make the alpha channel, if not just shout :wink: )
map it as normal with the UV editor and then select the faces to use the alpha channel. in the face buttons beneath the small green ones for collosion, light, halo etc click the pinkish(?) one saying alpha. assuming the image has a correct alpha channel they should now adopt the transparency

cheers
Piran


(PlantPerson) #3

Sorry, I don’t know how to make the alpha channel…
and I’m not sure I have any drawing programs which can save tga, but i’ll check.


(Piraniac) #4

hey, no probs (this may get a little long, but what the hey :wink: )
do you have GIMP? if not get it here -> http://www.gimp.org/ ,this will allow you to create alpha channels and save TGAs (oh, if your using 2.25, you can also use 32 bit PNG’s, which i think work better)

ok:-

  1. create your image, in whatever package you want then create a black and white (greyscale) version of the same image. this will act as your alpha channel, the black parts are transparent, white opaque and the greys inbetween varying degrees to transparency. of course, your alpha channel could be a completely different image, depends on what your doing

  2. load them into GIMP, then R-click (on the main image) then go -> Image->Mode->Decompose. this splits the image into its colour channels (R, G and B) and creates a seperate greyscale for each

  3. make sure your alpha image is a greyscale then R-click on one of the colour channel images->Image->Mode->Compose

  4. in the dialog box that comes up select RGBA from the left side, then in
    the drop-down boxes select the individual images to make up the final composition (if any aren’t displayed in the list, make sure they are all greyscale - its in the R-click menu somewhere)

  5. click OK and a new image should be created - complete with a nice checkered backdrop showing through the transparent parts. If the colours are screwy, check you put the right greyscale in the corresponding colour channel.

  6. finally (yey!) R-click and save your image, add .TGA to the name and GIMP will automatically save as a targa, with alpha intact.

then just map as normal in blender
i only use GIMP to create the alpha channels, so if any pro users know a better way then feel free to correct me!

hope this helps :slight_smile:
Piran


(z3r0 d) #5

Split your blender window (it appears it may be already)
Make one of the windows the image window
go into texured mode [alt+z]
select all of the faces of your sphere
choose your texture in the image window
in the paint buttons press at least the [tex] [alpha] buttons

I hope that solves your problem.