Transparent material w/ visible image map


(rknop) #1

Here’s my deal: I’ve got an object which I want to be mostly transparent, except for some spots. I’ve made up an image map which is a PNG; the PNG Is transparent everywhere excpet where I want color.

Now I want to map this to a sphere so that where there is color, that color shows up, but everywhere else it is transparent. The painting should only be on the surface of the sphere.

How does one do this? I’ve figured out to do UseAlpha in the texture block, so that I get the colored bits of the image map on top of the material’s underlying color. However, when I turn the Alpha of the material all the way down, the texture colors go away as well. How do I define the material’s underlying color as “transparent”, with the spots on the image map to be painted on top?

Thanks,

-Rob


(RipSting) #2

I’m not sure about Blender’s native support for any alpha channels in .png files. Have you checked the green “Alpha” button in the material settings for the texture (In the same group of buttons that has “Col”)?

If that doesn’t work, you’ll need to make a separate grayscale image that is an image of only the alpha channel (black = transparent, white = opaque).

  1. Assign the color image to the first material texture channel.

  2. Assign the grayscale image to the second texture channel.

  3. Go to the texture buttons and select the second channel (if it isn’t already).

  4. Click “CalcAlpha”

  5. Back in the material buttons, uncheck “Col” and instead check “Alpha”

  6. Enable ‘Ztransp’ and set the Alpha slider to 0


(rknop) #3

That part actually works fine.

Have you checked the green “Alpha” button in the material settings for the texture (In the same group of buttons that has “Col”)?

I had, but only got a mess. What I hadn’t yet tried was doing that and sliding the material Alpha slider to 0. Those two together achieved the effect I was looking for.

Thanks for the tip! Now if only I can get this animation put together before I mean to use it in my intro astronomy class…

-Rob