How to make a mask for voronoi texture (with randomness)? click to enlarge
I created mask from gradient texture with rgb mix node but it cuts some voronoi cells in half.
edit: i need the voronoi position to act as a mask..so it didn't cut the voronoi cells.
any other solution is also great if it didn't cut the cells.
my english is bit rough..feel free to edit it
The new Voronoi texture conveniently gives you a 'Position' output, which gives you (in 2D ) the X and Y coordinate of the center of a shading-point's cell.
So, if you don't want to cut your circle-'pixels' in half, you can use the distance of the whole cell from the texture space's origin to create a mask of whole cells, rather than the texture space itself.

I've scaled the whole texture down, so the cell-resolution is high enough to capture some circular curvature.