Ridged Multifractal Noise?

[desdemoli]

Hello. Playing around with the menu for texture generation (where you can put in mathematical functions etc) I was wondering if there was a way to create "Ridged Multifractal Noise". This type of noise is often used to generate heightmaps, bumpmaps, or textures for digital cartography, but unfortunately I'm completely oblivious to the whole math-side of such things.

I know in PS the usual technique would be to Render Clouds, and overlay several layers of Difference Clouds, but even that would not create proper ridged multifractals.

 

Anyway, I guess what I'm really looking for is a tutorial that goes in-depth of what different settings can do for noise.

 

Maybe someone can help.

[James Ritson]

Hi @desdemoli, from reading various discussions and threads about it, ridged multifractal noise appears to be perlin noise modified by an absolute function and inverted. I make no guarantee as to whether this works, but I believe you can do both using a live Procedural Texture filter. Add a new equation field and enable the RGB channels for it, then try:

1-abs(perlinsc(rx/200,ry/200,7,0.6))*0.5

Here's a screenshot of what it looks like:

 

However, there's this quote from a StackOverflow thread:

Quote

That assumes that the perlin noise generator generates the values in range <-1,1> (or another range centered on 0). ~50% of the pixels are expected to have value greater than 0 and ~50% are expected to have value less than 0.

The ABS causes sharp ridges to be created where the 0 is, since all the bilinear/trilinear interpolation would make sure that there used to be a smooth slope passing through the 0 value.

 

For perlin noise with values in the range of -1 to 1, you would want to use a harmonic perlin noise function, so the equation would need to be adapted like so:

1-abs(perlinhsc(rx/200,ry/200,7,0.6))*0.4

And another screenshot:

 

You will want to experiment with the multiplication value at the end—I lowered it to 0.4 for the harmonic perlin noise example.

It's also possible to adapt the comprehensive Perlin Noise preset that ships with the app (not Simple Noise, but the Perlin Noise preset) like so:

 

var v=vec2(rx,ry)*cells/w; tocui(1-abs(perlinhsc(v,oct,pers))*cont)+br

 

You can then use the parameters such as Octaves, Persistence, Cell count etc whilst having the ridged multi fractal perlin noise—at least that's what I think would happen.

Hope that helps!