When we apply a texture with an alpha map to our model, it becomes see through to the other pieces. For instance, the eye is a textured sphere and while the texture is set to transparent, you can see the entire sphere very clearly through the head mesh.
We are using a 2048 by 2048 png texture with a normal map of the same size on unity 3.x.
I think additive blending might not be appropriate, I know it’s used for particles and bright stuff and I’m not sure if it can produce black. Either way you should try a different blending mode, I think the right one is called alpha blending or mixed.
It’s the shader, the transparent shader gives transparent.
I think what you want is the transparent/cutout shader, this one has a slider where you can set what alphavalue counts as see through. You want that to be slightly higher than zero.