feat: actors stage 2

engine/scene/trees/Oak.ts

@@ -0,0 +1,53 @@
+import { Vec3 } from "../../math/Vec3"
+import type { Mesh } from "../Mesh"
+import type { Tree, TreeSpecies } from "../Tree"
+import { blob, lerp, limb, TAU, rng } from "./treekit"
+
+// Oak: short tapered trunk, a couple of branches, a broad cluster of rounded canopy
+// blobs (bushy, wider than tall). Trunk = brown bark, foliage = oak leaf.
+
+function build(tree: Tree, trunk: Mesh, leaves: Mesh, lod: "full" | "impostor"): void {
+  const base = tree.position
+  const g = tree.growth
+  const rand = rng(tree.seed)
+  const h = lerp(0.8, 7, g)
+  const rTrunk = lerp(0.04, 0.32, g)
+  const forkY = base.y + h * 0.5
+  const canopyY = base.y + h * 0.72
+  const blobR = h * 0.3
+  if (lod === "impostor") {
+    // One low-poly blob on a stubby trunk -- reads as an oak at distance.
+    limb(trunk, base, { x: base.x, y: forkY, z: base.z }, rTrunk, rTrunk * 0.6, 3)
+    blob(leaves, { x: base.x, y: canopyY, z: base.z }, blobR * 1.15, rand, 4, 2)
+    return
+  }
+  limb(trunk, base, { x: base.x, y: forkY, z: base.z }, rTrunk, rTrunk * 0.6, 5)
+
+  const spread = h * 0.32
+  // Central blob plus, as it grows, a couple offset ones -> broad bushy crown.
+  const blobs = 1 + Math.round(g * 2)
+  for (let i = 0; i < blobs; i++) {
+    const angle = rand() * TAU
+    const rad = i === 0 ? 0 : spread * (0.5 + rand() * 0.5)
+    const center = {
+      x: base.x + Math.cos(angle) * rad,
+      y: canopyY + (rand() - 0.4) * spread,
+      z: base.z + Math.sin(angle) * rad,
+    }
+    blob(leaves, center, blobR * (0.7 + rand() * 0.4), rand)
+  }
+  // Grown oaks throw out a few branches, each tipped with a leaf tuft.
+  if (g > 0.55) {
+    const branches = 2 + Math.round(rand())
+    for (let i = 0; i < branches; i++) {
+      const angle = rand() * TAU
+      const dir = Vec3.normalize({ x: Math.cos(angle), y: 1.2, z: Math.sin(angle) })
+      const start = { x: base.x, y: base.y + h * 0.42, z: base.z }
+      const end = Vec3.add(start, Vec3.scale(dir, h * 0.3))
+      limb(trunk, start, end, rTrunk * 0.4, rTrunk * 0.2, 4)
+      blob(leaves, end, blobR * 0.6, rand)
+    }
+  }
+}
+
+export const oak: TreeSpecies = { kind: "oak", trunk: "bark", foliage: "leaf", build }