When Mixing two Shaders, how would one have a more organic, wiggly transition, instead of a hard line?

Question

This node setup, disregarding the Vector Curve which I am failing to use, mixes two Shaders together, but with a long enough mesh, a hard line is very obvious. Here it is marked by blue.

How would one break this hard line into something more organic, wiggly, and speckled as indicated by red?

Answer 1

You can distort the gradient with a Noise texture

1. Noise texture to control the scale of the noise
2. Vector Math > Multiply to control the amount of distortion
3. Color Ramp to control the gradient position

Answer 2

Instead of using a vector curve, try displacing the whole vector with random noise - it will make it procedural and non repetitive (it will also work with a handpainted texture mask).

For the speckles use Musgrave Texture. You may limit specles placement with a ramp.

Tweak the scales and ramps to make it suit your needs better.

Answer 3

Try adding Voronoi texture to the gradient texture of the blend coefficient.