To register a Galaxy, you need to create a JSON file at data/corewithstuff/cws_galaxies/galaxyname.json

Example JSON

{
  "id": "modid:galaxy_name", // Galaxy registry ID. Optional; without it, the JSON filename becomes the ID.
  "display_name": "Galaxy Display Name", // Name shown to players.
  "universe": "modid:universe_name", // ID of the universe containing this galaxy.
  "space_dimension": "modid:space_dimension", // Dimension you are sent to when you fly into the galaxy.
  "render_dimension": "modid:some_dimension", // Dimension the galaxy is drawn in. Omit it to draw in the universe's own dimension.
  "removed": false, // True deletes this galaxy. Only "id" is read alongside it.

  "position": [0.0, 512.0, 0.0], // Galaxy center [x, y, z] in the dimension it is drawn in.
  "entry_position": [0.0, 800.0, 0.0], // Optional system-center fallback position.

  "type": "barred_spiral", // spiral, barred_spiral, elliptical, irregular, or ring.
  "size": 18000.0, // Galaxy width in blocks. Minimum is 10, but small galaxies are invisible from a distance.
  "primary_color": "#FF6BCBFF", // Main arm color in RGB or ARGB format.
  "secondary_color": "#FF9270FF", // Secondary arm, nebula and cluster color.
  "core_color": "#FFFFE9C0", // Galaxy core color.
  "rotation_speed": 0.0035, // Galaxy rotation rate. Degrees per second is this value times 12. 0 stops rotation.
  "tilt": 20.0, // Galaxy inclination in degrees.
  "arm_count": 4, // Number of arms. Valid range: 1-8.
  "brightness": 1.2, // Galaxy emission multiplier. Minimum is 0.05.
  "seed": 1337, // Star placement seed.
  "enter_radius": 6200.0, // Distance from the galaxy center that triggers entry. Keep it below half of size. Minimum is 16.

  "system_exit_mode": "button", // button, radius, height, hybrid, button_radius, button_height, button_hybrid, or disabled.
  "system_exit_radius": 0.0, // Horizontal boundary used by radius modes. 0 disables it.
  "system_exit_height": 0.0, // Vertical boundary used by height modes. 0 disables it.
  "system_entry_distance": 12000.0, // Arrival distance from the system center. Minimum is 64.

  "systems": [
    "Sol", // System display name. Matching is case-insensitive.
    "Alpha Centauri"
  ],

  "planets": [
    "modid:planet_dimension", // Planet DIMENSION ID.
    "modid:moon_dimension", // Moon DIMENSION ID.
    "modid:star_dimension" // Star DIMENSION ID.
  ],

  "planet_files": [
    "modid:planet_name", // Planet JSON ID: data/modid/cws_planets/planet_name.json.
    "modid:moon_name", // Moon JSON ID.
    "modid:star_name" // Star JSON ID.
  ]
}