meat/game/actors/trees/Spruce.ts

import type { Mesh } from "engine/scene/Mesh"
import type { Material } from "engine/render/Material"
import type { Prefab } from "engine/scene/Prefab"
import type { Tree } from "../Tree"
import { cone, lerp, limb, rng } from "./treekit"

// Spruce: tall thin trunk under stacked cones that narrow to a point (tiered, taller
// than wide). Trunk = brown bark, foliage = spruce needle.

export type Spruce = Prefab<Tree>

export namespace Spruce {
  export function create(trunk: Material, foliage: Material): Spruce {
    return {
      position: (tree) => tree.position,
      bakeNear: (tree, batch) =>
        build(tree, batch.mesh(trunk), batch.mesh(foliage), "full"),
      bakeFar: (tree, batch) =>
        build(tree, batch.mesh(trunk), batch.mesh(foliage), "impostor"),
      collider: treeCollider,
    }
  }

  function treeCollider(tree: Tree) {
    if (tree.growth <= 0.35) {
      return null
    }
    const radius = tree.growth * 0.2 + 0.15
    return {
      shape: "box" as const,
      minX: tree.position.x - radius,
      maxX: tree.position.x + radius,
      minZ: tree.position.z - radius,
      maxZ: tree.position.z + radius,
      top: tree.position.y + 3,
      standable: false,
    }
  }
}

function build(
  tree: Tree,
  trunk: Mesh,
  needles: Mesh,
  lod: "full" | "impostor",
): void {
  const base = tree.position
  const g = tree.growth
  const rand = rng(tree.seed)
  const h = lerp(0.6, 9, g)
  const rTrunk = lerp(0.03, 0.2, g)
  const impostor = lod === "impostor"
  limb(
    trunk,
    base,
    { x: base.x, y: base.y + h, z: base.z },
    rTrunk,
    rTrunk * 0.25,
    impostor ? 3 : 5,
  )

  // Stacked cones: widest low, shrinking to a point up top -> conical tiers. The
  // impostor keeps the first two tiers at low sides (same seed => aligned).
  const tiers = impostor ? 2 : 2 + Math.round(g * 3)
  const sides = impostor ? 4 : 6
  const bottom = base.y + h * 0.1
  const span = h * 0.9
  for (let i = 0; i < tiers; i++) {
    const t = i / tiers
    const y = bottom + t * span * 0.82
    const radius = lerp(h * 0.3, h * 0.05, t) * (0.9 + rand() * 0.2)
    const coneH = (span / tiers) * 1.9
    cone(needles, { x: base.x, y, z: base.z }, coneH, radius, sides)
  }
}