Make partsパーツを作る

{
  "slot": "turbo",
  "turbo": {
    "boost": 0.50,
    "spool_from": 0.30,
    "spool_full": 0.65,
    "spool_rate": 2.0
  }
}

• boost — extra torque at full boost (0 to 1.5)
• spool_from / spool_full — where boost starts and where it is full, as a fraction from idle (0) to the rev limit (1). Bigger turbos sit higher
• spool_rate — how fast boost builds (0.1 to 20). Smaller means more lag
• Anything you leave out takes roughly stock-turbo values

The two bundled turbos, for reference:

List car ids in cars (a turbo only for a diesel, say). Leave it out and every car can fit it.

{
  "slot": "turbo",
  "cars": ["mypack:prado"],
  "turbo": { "boost": 0.4 }
}

The sound belongs to the car, not the part: set "blowoff" in sounds in the car's vehicles/<car>.json (chapter 7 of the Car guide).

• No "Blow-off" tab — no turbo is fitted. Fit a turbo first
• The log says the turbo part has no turbo — add "turbo": { ... } (without it you get roughly stock-turbo values)
• Nothing changes on the car's body — turbos and blow-off valves have no looks yet (only the parts-screen icon and the TURBO lamp on the gauges)

A part whose effect is fixed (a duck tail, say) takes a single number. data/mypack/car_parts/ducktail.json:

{
  "slot": "rear_wing",
  "aero": { "rear": 0.25 }
}

A part whose effect players can adjust with the parts screen's "Angle" slider (a GT wing, say) takes [min, max]. Add front if it should press the front too. data/mypack/car_parts/gt_wing.json:

{
  "slot": "rear_wing",
  "aero": {
    "rear": [0.6, 1.6],
    "front": 0.1,
    "angle": 0.4
  }
}

• front / rear — how hard it presses the front and rear down. Bigger is stronger (0 to 3). 1 is about 190 kg at 200 km/h
• Guide: 0.3–0.6 in total for a road car with a wing, 2–3 for a GT race car
• angle — where the "Angle" slider starts (0–1, default 0.5). The angle changes driving only; the object does not move
• More downforce makes fast corners quicker but lowers top speed. Drag follows automatically, so there is nothing to write for it
• More at the front turns in harder (oversteer); more at the rear is more stable (understeer)

The parts screen shows the part's downforce and how balance, grip and estimated top speed change.

part_<part> (e.g. part_gt_wing) works too. For any other name, map it in the car's vehicles/<car>.json:

"parts": {
  "mypack:twin_muffler": { "show": ["part_exhaust-twin", "part_exhaust-twin_tip"] }
}

Only names starting with part_ are allowed in show.

Put them in the car's spec, data/mypack/cars/<car>.json, at the top level next to values:

{
  "values": { "mass": 1250 },
  "default_parts": {
    "rear_wing": "mypack:s15_spoiler",
    "exhaust": { "part": "mypack:stock_muffler", "removable": false }
  }
}

• "Stock" in the parts screen becomes the default part. Slots with a removable default also get "None"
• "removable": false means it cannot come off. Use it for parts that would leave a hole
• It reaches cars already placed: change the default in the pack and existing cars follow

The game only shows or hides part objects that are already inside the car's OBJ. It draws the objects of the fitted parts and skips the rest. So:

• A part that is not in the OBJ cannot appear. You cannot ship a part as a separate file and add it later
• An object exported while hidden is not in the OBJ, so it cannot appear either
• Adding a part means exporting the car's OBJ again
• A parts-only pack cannot add body parts to someone else's car

• Don't export with objects hidden. With "Selected Only", hidden objects cannot be selected and drop out
• Make stock pieces separate objects too. Anything left merged into body stays, whatever is fitted
• Faces inside a part with a light_tail material light up with the part (chapter 3 of the Car guide)
• cars limits which cars can fit it. The display name is part.<pack>.<part>

Add a looks JSON, assets/mypack/car_parts/titanium.json (same file name as the definition):

{
  "exhaust": {
    "pitch": [0.85, 1.00],
    "volume": 1.2,
    "tone": 0.3
  }
}

• pitch — pitch multiplier; below 1 is deeper. Written as [min, max], the parts screen's "Deepness" slider moves within it
• volume — volume multiplier (0 to 2)
• tone — where the "Deepness" slider starts (0 = highest, 1 = lowest; default 0)
• Going down works well to about 0.78. Going up barely works (for a high-pitched exhaust, see "Use your own sound" below)

1. Add the sound (OGG, mono, a seamless loop): assets/mypack/sounds/titanium_exhaust.ogg
2. Declare a sound event in your pack's assets/mypack/sounds.json:

   {
     "titanium_exhaust": {
       "sounds": [{ "name": "mypack:titanium_exhaust" }],
       "attenuation_distance": 64
     }
   }

3. Point to it from exhaust in the looks JSON:

   {
     "exhaust": { "sound": "mypack:titanium_exhaust" }
   }

To keep the pitch rising at high revs, also make a one-octave-up copy and point "sound_high" at it; sound_tools/make_octave_up.py makes one. More on making sounds in chapter 7 of the Car guide.

Make the stock exhaust a separate object too (e.g. part_exhaust-stock), give it a part, and make it a default part at the top level of the car's spec data/mypack/cars/<car>.json. If removing it would leave just a hole, make it non-removable:

{
  "values": { ... },
  "default_parts": {
    "exhaust": { "part": "mypack:stock", "removable": false }
  }
}

More on default parts in chapter 2, "Have it fitted from the start".

• No "Exhaust" tab — the object is not in the OBJ. Check it was not hidden when you exported
• Your sound does not play; it is the usual one — the sound name is missing from sounds.json. A warning is in the log
• pitch above 1 does not raise it — Minecraft's pitch ceiling. Replace the source with a higher one via sound