52 lines
2.1 KiB
TypeScript
52 lines
2.1 KiB
TypeScript
import { Vec3 } from "../../../engine/math/Vec3"
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import type { Mesh } from "../../../engine/scene/Mesh"
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import type { Tree, TreeSpecies } from "../Tree"
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import { blob, lerp, limb, TAU, rng } from "./treekit"
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// Silver birch: tall, slender, near-straight trunk under an airy, high, slightly
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// drooping canopy -- a lean silhouette between the broad oak and conical spruce.
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// Trunk = white birch bark, foliage = oak leaf (the white trunk carries the read).
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export const birch: TreeSpecies = { kind: "birch", trunk: "birch", foliage: "leaf", build }
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function build(tree: Tree, trunk: Mesh, leaves: Mesh, lod: "full" | "impostor"): void {
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const base = tree.position
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const g = tree.growth
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const rand = rng(tree.seed)
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const h = lerp(1, 8.5, g)
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const rTrunk = lerp(0.03, 0.16, g)
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const canopyY = base.y + h * 0.75
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const blobR = h * 0.22
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if (lod === "impostor") {
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limb(trunk, base, { x: base.x, y: base.y + h * 0.9, z: base.z }, rTrunk, rTrunk * 0.5, 3)
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blob(leaves, { x: base.x, y: canopyY, z: base.z }, blobR * 1.1, rand, 4, 2)
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return
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}
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limb(trunk, base, { x: base.x, y: base.y + h * 0.88, z: base.z }, rTrunk, rTrunk * 0.35, 5)
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const spread = h * 0.22
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// Sparse small blobs clustered high, biased downward so the crown droops.
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const blobs = 2 + Math.round(g * 2)
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for (let i = 0; i < blobs; i++) {
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const angle = rand() * TAU
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const rad = i === 0 ? 0 : spread * (0.5 + rand() * 0.5)
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const center = {
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x: base.x + Math.cos(angle) * rad,
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y: canopyY + (rand() - 0.6) * spread,
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z: base.z + Math.sin(angle) * rad,
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}
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blob(leaves, center, blobR * (0.7 + rand() * 0.4), rand)
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}
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// Grown birches trail a few thin, near-horizontal drooping twigs.
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if (g > 0.5) {
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const branches = 2 + Math.round(rand())
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for (let i = 0; i < branches; i++) {
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const angle = rand() * TAU
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const dir = Vec3.normalize({ x: Math.cos(angle), y: 0.6, z: Math.sin(angle) })
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const start = { x: base.x, y: base.y + h * 0.7, z: base.z }
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const end = Vec3.add(start, Vec3.scale(dir, h * 0.22))
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limb(trunk, start, end, rTrunk * 0.4, rTrunk * 0.15, 4)
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blob(leaves, end, blobR * 0.55, rand)
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}
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}
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}
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