ya mean like when an object has an alpha channel in its texmap, the thing behind the figure would show thru? meaning part of the figure would be invisible? I reckon it would only work with a one-sided object, as any backfaces would screw things up. as ya noted, using the blender node is the way they usually do it for lettering, tattoos or whatnot. I've also seen some of 'em recommend using the colour ramp, but that is overkill and inelegant IMVHO.