PlanetData Reference

PlanetData Reference

This page is the complete field reference for PlanetData JSON files, loaded from data/<namespace>/orrery_planets/*.json.

Top-level fields

Field	Type	Required	Description
dimension	string (resource key)	Yes	The dimension this planet corresponds to, e.g. "orrery:eris". Must match an existing dimension definition.
planet_name	string	Yes	Internal identifier used by Northstar's planet-name lookups (rocket destinations, etc.).
gravity	double	Yes	Surface gravity as a multiple of Earth's gravity. 1.0 = Earth-normal, 0.084 = Eris (~8.4%). Also drives fall damage scaling — see below.
has_oxygen	boolean	Yes	Whether the planet has a breathable atmosphere.
temperature	int	Yes	Surface temperature value, consumed by Northstar's temperature systems.
atmosphere_cost	int	Yes	Cost value for atmosphere-related Northstar mechanics.
computing_cost	int	Yes	Computing cost for navigating/landing on this planet.
engine_constant	double	Yes	Engine performance constant used in rocket travel calculations.
sun_multiplier	float	Yes	Northstar's internal sun-strength multiplier (e.g. solar panel output). Distinct from sky.sun_brightness.
has_sky	boolean	Yes	Whether Orrery's custom sky renderer (PlanetSkyMixin) handles this dimension's sky at all. If false, vanilla sky rendering applies.
can_see_sky_at_day	boolean	Yes	Whether the sky is visible during the in-game day cycle.
has_weather	boolean	Yes	Whether rain/snow weather can occur on this planet.
seed_offset	long	Yes	Offset applied to the world seed for this dimension's terrain generation. Ensures different planets sharing a base seed don't generate identical terrain.
is_in_orbit	boolean	Yes	Marks this dimension as an orbit-type location for Northstar's systems (as opposed to a surface).
wind_multiplier	float	Yes	Scales wind-related effects, where applicable.
sky	object	Yes if has_sky is true	Nested object describing sky rendering — see below.

sky object fields

Field	Type	Description
has_stars	boolean	Whether stars render in the sky.
star_brightness	float	Base star brightness. See the note on the brightness formula below.
sun_brightness	float	Brightness multiplier (0.0–1.0+) applied to the rendered sun disc.

How fields are consumed

Gravity → fall damage

There is no separate fall damage field. PlanetFallDamageMixin computes effective fall distance as:

effectiveFallDistance = actualFallDistance * gravity

This effective distance is compared against the vanilla 3-block safe-fall threshold. A planet with gravity: 0.084 lets players fall roughly 12x further than on Earth before taking damage, since the effective distance is scaled down proportionally.

Star brightness formula

PlanetSkyMixin computes rendered star brightness as:

renderedBrightness = sky.star_brightness - (vanillaStarBrightness(partialTick) * 0.5)

vanillaStarBrightness follows the normal Minecraft day/night cycle (0 during day, ramping up at night). This means:

• During the in-game "day", renderedBrightness ≈ sky.star_brightness (stars near full configured brightness)
• During the in-game "night", renderedBrightness is reduced by up to 0.5 This is intentional — on an airless world, the day/night cycle doesn't represent atmospheric scattering, but the formula still produces a subtle variation tied to the cycle for visual interest.

Sun rendering

If has_sky is true, a small sun disc is rendered using the northstar:textures/environment/baresun.png texture, tinted by sky.sun_brightness (applied as an RGB multiplier, with alpha fixed at 1.0). A sun_brightness of 1.0 is full white; lower values dim the sun toward black.

sun_multiplier vs sky.sun_brightness

These are separate fields with separate purposes:

• sun_multiplier — read by NorthstarPlanetsMixin, affects Northstar's gameplay mechanics (e.g. solar panel power generation)
• sky.sun_brightness — read by PlanetSkyMixin, purely visual, affects how bright the rendered sun disc appears A planet could theoretically have a visually bright sun (sky.sun_brightness: 1.0) but contribute nothing to solar power (sun_multiplier: 0.0), or vice versa. Set both according to what makes sense for the planet — for Eris, both are low/zero since it's extremely distant from the Sun.

Validation and error handling

PlanetDataLoader parses each file with PlanetData.CODEC. If a file fails to parse:

• The specific file is skipped (logged as [Orrery] Failed to parse planet <id>: <error>)

• Other valid files in the same reload are still loaded normally

• The planet from the failed file will not appear in /orrery or be recognized by any Mixin Common parse failures:

• Missing required fields

• Wrong types (e.g. a string where a number is expected)

• Malformed or missing sky object when has_sky is true — note that sky is part of the top-level codec group, so a malformed sky object fails the entire file's parse, not just the sky portion

Full example (Eris)

{
  "dimension": "orrery:eris",
  "planet_name": "eris",
  "gravity": 0.084,
  "has_oxygen": false,
  "temperature": -230,
  "atmosphere_cost": 0,
  "computing_cost": 900,
  "engine_constant": 15.0,
  "sun_multiplier": 0.0,
  "has_sky": true,
  "can_see_sky_at_day": true,
  "has_weather": false,
  "seed_offset": 9,
  "is_in_orbit": true,
  "wind_multiplier": 0.0,
  "sky": {
    "has_stars": true,
    "star_brightness": 1.0,
    "sun_brightness": 0.6
  }
}