Thanks for the compliment.
The fractals that I work with are called quaternion Julia sets.
QuasZ is a GUI fractal generator that supports export to 3D file formats (ie. OBJ, STL) . It's $30 -->
https://www.mysticfractal.com/QuaSZ.html
Julia 4D 2 is a GUI fractal generator that supports export to OBJ. I wrote it about 10 years ago and it's cost-free and in the public domain. You may need to download a DirectX 9.0c runtime to run this app -->
https://github.com/AnthonyNystrom/Julia-4D I've included a compiled version in a zip file attachment to this post.
I also wrote my own commandline fractal generator from scratch. It's cost-free and in the public domain and supports export to STL format. It's also GPU-accelerated, so it's much faster than the two other apps listed above -->
https://code.google.com/p/qjs-isosurface/ I've included a compiled version in a zip file attachment to this post. You will need to download the GLUT and GLEW libraries to run this app.
I generated the model using my commandline software. The iterative equation that I used for this model is z' = sin(z) + c*sin(z). I use this equation to test which points along a 3D grid belong in the fractal set. Once those tests are complete, I use Marching Cubes to generate the final triangle mesh.
A really good introduction to quaternion fractals can be found at:
https://paulbourke.net/fractals/quatjulia/
A really good introduction to Marching Cubes can be found at:
https://paulbourke.net/geometry/polygonise/
A really good introduction to quaternion math can be found at:
https://www.theworld.com/~sweetser/quaternions/intro/tools/to ols.html
If you're not into quaternions, a really good introduction to 2D fractals can be found at:
https://www.codeproject.com/Articles/650821/Fractals-in-theor y-and-practice (see: Julia set).
Hope that answers your questions. If you'd like more detail on a certain part of my explanation, then please feel free to ask.
For the record, the model was printed using White Strong & Flexible plastic, and it's downright awesome to behold. Shapeways rocks!!!