Adding Noise along lines using nodes

Question

My goal is to add procedural grass patches along the crevices of tiles. I have a tile pattern as below

So, is it possible to add noise along those black lines so that they can be colored green to give some grass patch effect?? To my knowledge I can only add Noise inside the black lines by using mix RGB node with fac as the tile pattern and noise node as one of the inputs as shown below.

. But this isn't what I need.. i need the noise to extend beyond the line boundaries a bit more (not just inside). Any ideas how to achieve this??

Answer 1

I think you will need some sort of distance function from the cracks between the bricks. If your herringbone is procedural, that could be maths, inside the node tree. If it is an image texture, then blurring will do a pretty good job. You could blur the texture in an external application, or by putting it through Blender's own compositor:

.. trying to get a good range of greys for maximum flexibility. Then..

.. (Left) it can be inverted and adjusted, using a Color Ramp... Your Noise, (Center) can be put through another Color Ramp. When the two are Mix RGB > Multiplied, (Right,) you begin to see how the bleed-mask appears. It can be further adjusted, put through a 'Greater Than' threshold, or a softer threshold, using another Color-Ramp, or Map Range.

The Brick shader (Left), and the Grass shader (Center) can be mixed using the resulting mask (right).

These are the nodes which produce the mask:

The result: