Can be a solution. But, I still think that a simple shader could be used easily. The problem is that I don't know to much about shaders..

I tried to adapt some shaders, as the multi-texture terrain shader, but I had no success.

I think the scheme is simple, like two textures, first black, to be transparent, second a simple grid - small, tiled according to the scale set (as the multi-texture terrain).

The point is, how I translate this sentence to a shader code...

Anyway, thanks for helping.