if all you need are masks like that you can do that with coordinate based masks. for example take the red component of the uv coords, subtract 0.5 from it and ceil it. this should give you a very crisp mask and might solve your problem.
if all you need are masks like that you can do that with coordinate based masks. for example take the red component of the uv coords, subtract 0.5 from it and ceil it. this should give you a very crisp mask and might solve your problem.