The Galaxy Spatioplotter generates a galaxy using a newly developed algorithm.
It uses three basic observation and theories:
  • Galaxy Rotation Curve
  • Stochastic Self-Propagating Star Formation (SSPSF)
  • Density Wave (DW) theory

Combining those three theories, it can generate various shapes of galaxies.

Galaxy Rotation Curve
You can refer to Wikipedia the detail of the Galaxy Rotation Curve.
This app can define the rotation curve using spline curve with 5 points.

The SSPSF (stochastic self-propagating star formation) model
This app can define right now only the probability of propagation and the radius of neighbors.
All other parameters are difficult to figure out (any small change can just produce none), and I used fixed values that I found it works.

SSPSF generate general structure of spirals.

Please refer to Wikipedia for more detail SSPSF model
The paper I referenced is here:
Title: Stochastic star formation and spiral structure of galaxies
Authors: Gerola, H. & Seiden, P. E.
Journal: Astrophysical Journal, Part 1, vol. 223, July 1, 1978, p. 129-135, 137, 139.
Bibliographic Code: 1978ApJ...223..129G

Density Wave (DW) theory
For a grand design structure, the app uses the Density Wave theory.
Please refer to Wikipedia ensity wave theory

DW example:

The DW generate grand design structure.