SupplyTruck

SupplyTruck

The weapons truck: drive into the back, pick a refit, roll back out.

What it does

supplyTruck.dispatch brings a tractor and its trailer onto the slow lane, arriveAhead metres in front of the player. The tractor is an ordinary car with an AutoRunnerDriver in the truck role. The trailer is dragged behind it.

Drive into the back of the trailer, roughly lined up. Full throttle is fine; coming in sideways is a crash. The car turns ghost, rolls to the middle of the trailer over loadSeconds and goes out of sight. While it rides inside, the HUD offers up to three refits:

• missiles: +3
• oil slicks: +5
• smoke screens: +5
• guns: one level up
• armour: a full repair

A weapon you are full of is never offered. Armour only shows up below 95% health, unless there is nothing else to offer. Pick one with the chooseKeys, or the first offer is fitted after menuSeconds. Then the car rolls out of the tail a little slower than the truck, and the truck speeds off and goes back to its pools.

If the player never docks, the truck waits patience seconds, or gives up at once if the player drives 70 m past it or drops 160 m behind.

supplyTruck.deliver uses the same truck for a new life: the new car rides inside for deliverSeconds and is let out behind it.

Use it in a scene

{
  "Game": {
    "components": {
      "SupplyTruck": {
        "player": "Player",
        "cabPool": "truckCab",
        "trailerPool": "truckTrailer"
      }
    }
  },
  "TruckCabBlueprint": {
    "tags": ["car", "truck"],
    "components": {
      "Pool": { "name": "truckCab", "size": 1 },
      "MeshPrimitive": {
        "primitive": "box",
        "width": 2.4,
        "height": 2.8,
        "depth": 7
      },
      "CarDrive": { "keyboardControlled": false, "maxSpeed": 64 },
      "CarCollision": { "mass": 9, "halfWidth": 1.2, "halfLength": 3.5 },
      "AutoRunnerDriver": { "role": "truck", "cruiseSpeed": 30 }
    }
  },
  "TruckTrailerBlueprint": {
    "tags": ["car", "truck", "trailer"],
    "components": {
      "Pool": { "name": "truckTrailer", "size": 1 },
      "MeshPrimitive": {
        "primitive": "box",
        "width": 2.4,
        "height": 2.6,
        "depth": 6.4
      },
      "CarDrive": {
        "maxSpeed": 80,
        "acceleration": 0,
        "braking": 0,
        "steerRate": 0,
        "keyboardControlled": false
      },
      "CarCollision": {
        "mass": 8,
        "halfWidth": 1.2,
        "halfLength": 3.2,
        "kinematic": true
      }
    }
  }
}

Give the trailer "kinematic": true on CarCollision, so a crash pushes other cars off it without fighting the hitch.

The trailer swings wide

The trailer is never driven. Each frame its nose sits on the tractor's hitch and its heading eases toward the tractor's:

  const L = Math.max(1, halfLength * 2);
  const heading = trailerHeading + (Math.abs(speed) / L) * Math.sin(d) * dt;
  const h = hitchPoint(cab, hitchBack);
  return { x: h.x - Math.sin(heading) * halfLength, z: h.z - Math.cos(heading) * halfLength, heading };

d is the angle between tractor and trailer. Speed times dt is the distance the truck moved, so the trailer turns by distance, not by time. For each trailer length of road, the angle shrinks by about two thirds, at any speed. A 6.4 m trailer at 30 m/s covers its own length in about 0.2 seconds. Through a bend the trailer lags the tractor and cuts inside its line, which is why a real semi swings wide.

The dock gate

Docking is a box behind the trailer's doors. The player's nose has to be in it, lined up, and closing:

export const DEFAULT_DOCK_GATE: DockGate = {
  // The trailer's half width (1.2) plus half a car: a car that overlaps the
  // doors by half its width is taken in. Any less and it clips the corner.
  halfWidth: 1.7,
  // Deep enough that a car closing at 30 m/s is seen inside it for a few frames
  // before its nose reaches the doors and CarCollision bounces it off.
  behind: 3,
  inside: 1.2,
  maxAngle: 0.55,
  minClosing: -4,
  // Full throttle (52 m/s) on a 30 m/s truck is 22: that has to dock.
  maxClosing: 30,
};

maxAngle is about 31 degrees. A player who aims at the back of the truck gets in. One who comes in at 45 degrees rams the trailer instead.

Settings

Events

Needs

• CarDrive moves the tractor, the trailer and the car inside.
• CarCollision gives the sizes, and its ghost tag lets the car pass through the doors.
• MeshPrimitive gives positions.
• HighwayRoad puts the truck in the slow lane and off any bridge.
• AutoRunnerDriver drives the tractor.
• AutoRunnerWeapons is read to pick offers, and takes the refit.
• Health is read for the armour offer, and takes the repair.
• KeyboardInput turns DOM key presses into keyboard.keydown on the bus, which is how the refit keys arrive.