Texturing Alpha

I was just wondering how to make planes "invisible" except for the part of the texture you want to show?

Cover them with the alpha channel and give the model an appropriate material.

where do i find the alpha channel? (im using 3ds max and photoshop)

In photoshop its quite simple.

Note:
+ When converting blp always convert it to a TGA file. Dont use bmp, gif or jpg.
+ Not every bit on a wc3 model can be alpha. There are a couple of material types: 2-color alpha, multi-color alpha, Normal and teamcolor.
Normal cannot be alphaed.
2-color alpha means that you can not alpha things "smoothly", meaning its either there or its not.
Multi-color alpha means that you can smoothly make things invisible. Verry rare, not a lot of models have this.
teamcolor is basically a multi-color alpha material, but areas you make invisible show up as teamcolor.
+Alpha channels are greyscale. White is visible, black invisible.

As far as i know, there is no direct way of seeing wich parts of the model are what material. Also, wc3vieuwer might sometimes show things correctly alphaed, but in-game it wont be.

Do:
+ Open the TGA file of the skin you wish to edit.
+ Open the "channels" window
+ Select the alpha channel.
If the texture doesnt have an inherit alpha channel, you can try creating one and naming it "alpha", but most likely, if the texture has no alpha channel, it wont have spots that cant be alphaed.
+Edit the alpha channel as you please.

Sometimes, the alpha channel is automatically synced with "invisible" areas of photoshop files. I dont know how, my photoshop just did it one day.