HighwayRoad

HighwayRoad

An endless highway grown from one seed number, so each run gets the same bends.

What it does

HighwayRoadComponent holds the seed and the shape of the road. HighwayRoad.core turns them into a plan: a centre line, a lane count per 380 m block, rivers with bridges, and towns. Every question about the road is a function of the seed and the distance, so it has one answer everywhere. The meshes, the trees, the AI cars and the crash tests all ask the same plan.

HighwayRoadSystem builds meshes only for the stretch around the followed car. It keeps a ring of 30 m chunk slots, two behind and eight ahead. When the car moves on, the slot that fell behind is rebuilt as the next chunk ahead.

Use it in a scene

{
  "Road": {
    "components": {
      "HighwayRoad": {
        "seed": 1983,
        "follow": "Player",
        "laneWidth": 3.7,
        "startLanes": 3,
        "bridgeChance": 0.32
      }
    }
  }
}

Call registerHighwayRoadExtension(adapter) from adapter/register.ts at bootstrap for the full look. Without it, each layer is drawn in one flat colour, and the look settings (the asphalt maps, paintGlow, the water) do nothing. The road plan works the same either way.

Road space

A car thinks in "how far along" (s) and "how far across" (u), not in world X and Z. The plan converts both ways. Here is the default road at the start line, where it has three lanes:

const plan = createRoadPlan({});
plan.laneOffset(0, 0);    // -3.7  lane 0, on the −X side
plan.laneOffset(0, 2);    //  3.7
plan.surfaceAt(6.5, 10);  // 'shoulder'
plan.surfaceAt(7.5, 10);  // 'verge'
plan.project(x, z);       // { s, u }, and plan.toWorld(s, u) goes back

Other components get the plan with findRoad(world) from HighwayRoad.defs. They never import the drawing System.

The centre line

The bends are not stored anywhere. The centre line is three sine waves added up, each with a phase picked from the seed:

    const w =
      0.74 * Math.sin(k1 * z + ph1) + 0.3 * Math.sin(k2 * z + ph2) + 0.07 * Math.sin(k3 * z + ph3);
    return p.curveAmplitude * c * w;

The longest wave is curveWavelength long. The other two are shorter, so the road wanders instead of repeating. c is how curvy the current block is. It eases from one block to the next. It is also zero for the first half of straightStart and fades in after, so a run never opens on a bend.

What a chunk holds

• Asphalt: the lanes and lighter shoulders, tinted per vertex so the tarmac is never one flat sheet, and a dark curb down each edge.
• Paint: a solid yellow line on the +X edge, a solid white one on the −X edge, and dashed white lane lines.
• Terrain: a gravel lip, a ditch, then rolling grass coloured by noise. It sinks to mud and river bed at a crossing.
• Water and structure (bridge parapets and piers) appear only where the chunk crosses a river. The water is close to a mirror, so it shows the scene's sky.

Next-door chunks share their edge row exactly, so there is no seam. At night the paint glows brighter so the lines still show.

Settings

Events

Needs

• MeshPrimitive: where the followed car is right now.