turbulence
turbulence 32,6,3,0,0


G'MIC
TURBULENCE

In theory, a call to turbulence is a call to turbulence 32,6,3,0,0. But a call to turbulence without any trailing parameters only works (for me, because I don't really know what I am doing) if I stop my code short and output to an implicit call to display instead of saving the lot to a file.


For the above image (in PowerShell), I used:

gmic `
  input 1000,250,1,3,0 `
  turbulence 32,6,3,0,0 `
  output image.jpg

• gmic
• Calls G'MIC.
• input 1000,250,1,3,0
• Creates a 1000x250 all-black three-color image.
• turbulence 32,6,3,0,0
• These are the default values.
• output image.jpg
• And finally, I save the file.

turbulence 32,6,3,0,0
turbulence radius, octaves, alpha, difference, mode


I am a fan of G'MIC, but the documentation sucks. I mean, it really sucks. For instance, the last parameter is mode. I assume (as I have not found the place in the documentation where it says) that mode represents the different algorithms which have been implemented for turbulence. And if it is indeed the case that mode is a listing of algorithms (is it), it would make sense to at least (at the very least) give a name to the different algorithms.

Anyway, in the absence of documentation, the best (in my ever so freakin' increasingly humble opinion) way to figure out what the different parameters do is via experimentation.

Radius

Unsurprisingly, radius controls the size of the splotches: the greater the radius... er, um, the greater the radius of the splotches.

But if you can tell what octaves controls, you are a better man, woman, child, or nascent AI than I.

Oh, before I move on, I should say that I have a preference (at least in the moment) for radius 100 over radius 1. And as such, that is the setting I shall use for the rest of images on this page.

Octaves

Thus (per the above images), I take octaves to denote the smoothness (or roughness) of the resulting image... the graininess of the turbulence... or perhaps, how many times the function (as determined by the mode) is applied iteratively.

And I was going to say how I liked the smoother image (octave=1) better. But it has less of what I would call turbulence. Certainly, changes to the next parameter seemed to have no effect if the image had already been smoothed out.

Alpha

The default is alpha=3, after which point the image becomes smoother and smoother, making it hard to tell the difference between octave=1 and alpha=5.

I really could not tell you what is happening here. But I do know that of the five, I'm liking alpha=2 the best. It looks like some sort of colourized telescopic image, perhaps of a gas cloud.

Difference

I did not note much qualitative difference between difference=-1 and difference=-10. In the trials I ran, negative values produce a lighter (more white) background (like the above) and zero or positive values elicited no change.

Mode

Unfortunately, I could not see much difference between any of the modes... certainly, not enough of a difference to waste the bandwidth posting near identical images. There was a slight difference in lightness. But not much. And if I had to chose a personal preference for any of the modes, I would choose the default of mode=0.

The Recap

• radius
• 0.0-∞: int or float
• size of splotches
  • larger numbers yield a larger radius
• octaves
• 1-12: int
• I assume this is the number of times the algorithm is applied.
• smoothness
  • larger numbers are rougher...
    • more nuanced
• alpha
• 0.0-∞: int or float
• looks to be a smoothing/sharpening function
• difference
• -10 to 10: int or float
• negative: lighter background
• positive: darker background
• mode
• 0-4: int
• presumably, the underlying algorithm
• I noted little difference between them

Other Functions

I originally started working on this page, as I was doing a write-up on rand, which led me to the various noise calls (noise, noise_hurl, noise_perlin, and noise_poissondisk).

So, any of those might be of use.

Certainly, they are what I am going to explore next.