controlling where tile random popping up

hegvbwkeuyrv

so im creating a brick wall, and i want to add CHIP damage. i already made a shape of the chip, now its just a matter of tiling it onto the brick surface. However i only want this chip damage appear on the edges of the brick. How can i achieve this look?

I tried using 5 transofrmation 2d and placing the crack one by one, but this is not in any way a procedural way of doing it

im thinking of maybe using curvature map? but i dont know how to utilize it

poopipe

 you can use the output of your tile random to drive placement of tiles in a tile sampler

hegvbwkeuyrv

can you specify which one? ive read the documentation and tried every input with my height map but nothing works

poopipe

Off the top of my head.. 

Assuming there's no tile mask  plugging the height into Displacement and Scale with a bit of randomisation should get you most of the way there

You probably want to mess with contrast on the inputs, maybe a distance node to restrict where they go.. 

hegvbwkeuyrv

distance ndoe? i thought that node was to make rocks with dilation right?

poopipe

it just draws a gradient between black and white areas - which is useful for a wide variety of things.