skatemakerpro/js/parkmath.js

// SKATEMAKER PRO — park math. The whole religion in one file:
// a park is DATA (elements list), and heightAt(x,z) evaluated from that data is the
// single source of truth for the visual mesh AND the collision. Same lesson as BOOKQUOY.
//
// Every element lives in a rotated local frame: u along the element, v across it.
//   u_dir = ( cos rot, sin rot )  in (x,z)
//   v_dir = (-sin rot, cos rot )  — ramps descend toward +v ("facing").

const clamp = (v, a, b) => Math.min(b, Math.max(a, v));
const sstep = t => { t = clamp(t, 0, 1); return t * t * (3 - 2 * t); };

// quarter-pipe transition: d = distance from the wall, r = radius. h(0)=r, h(r)=0.
export function tranny(d, r) {
  if (d >= r) return 0;
  if (d <= 0) return r;
  const q = r - d;
  return r - Math.sqrt(Math.max(r * r - q * q, 0));
}

function local(e, x, z) {              // world (x,z) -> element-local (u,v)
  const dx = x - e.x, dz = z - e.z, c = Math.cos(e.rot || 0), s = Math.sin(e.rot || 0);
  return [dx * c + dz * s, -dx * s + dz * c];
}

// ---------------------------------------------------------------- element kinds
// Each returns a height contribution (concrete = max of all). Bowls carve (override).
export const ELEMENT_KINDS = {
  quarter: {                            // straight QP, escalating radius, optional lump + deck
    label: 'Quarter Pipe',
    defaults: { len: 8, r0: 1.2, r1: 1.2, lump: 0, deck: 0.6 },
    height(e, x, z) {
      const [u, v] = local(e, x, z);
      if (Math.abs(u) > e.len / 2) return 0;
      let r = e.r0 + (e.r1 - e.r0) * sstep(u / e.len + 0.5);
      if (e.lump) r += e.lump * Math.sin(u * 0.9);
      if (v < -e.deck) return 0;
      if (v <= 0) return r;             // deck behind the coping
      return tranny(v, r);
    },
  },
  bank: {
    label: 'Bank',
    defaults: { len: 6, h: 0.9, run: 2.4, deck: 0.5 },
    height(e, x, z) {
      const [u, v] = local(e, x, z);
      if (Math.abs(u) > e.len / 2 || v < -e.deck || v >= e.run) return 0;
      return v <= 0 ? e.h : e.h * (1 - v / e.run);
    },
  },
  funbox: {                             // soft-skirted box (bookquoy funbox)
    label: 'Funbox',
    defaults: { hw: 2.5, hd: 1.2, h: 0.9, skirt: 1.6 },
    height(e, x, z) {
      const [u, v] = local(e, x, z);
      const d = Math.max(Math.abs(u) - e.hw, Math.abs(v) - e.hd);
      if (d <= 0) return e.h;
      if (d >= e.skirt) return 0;
      return e.h * (1 - d / e.skirt);
    },
  },
  ledge: {                              // sharp-sided plateau / manual pad / grind ledge
    label: 'Ledge / Pad',
    defaults: { hw: 1.5, hd: 0.8, h: 0.45 },
    height(e, x, z) {
      const [u, v] = local(e, x, z);
      return (Math.abs(u) <= e.hw && Math.abs(v) <= e.hd) ? e.h : 0;
    },
  },
  mogul: {                              // gaussian bump / volcano
    label: 'Mogul / Volcano',
    defaults: { h: 0.6, s: 2.4 },
    height(e, x, z) {
      const r2 = (x - e.x) ** 2 + (z - e.z) ** 2;
      return e.h * Math.exp(-r2 / (e.s * e.s));
    },
  },
  spine: {                              // back-to-back quarters along u
    label: 'Spine',
    defaults: { len: 8, r: 1.2 },
    height(e, x, z) {
      const [u, v] = local(e, x, z);
      if (Math.abs(u) > e.len / 2) return 0;
      const d = Math.abs(v);
      return d >= e.r ? 0 : tranny(d, e.r);
    },
  },
  pyramid: {                            // 4-sided bank pyramid with flat top
    label: 'Pyramid',
    defaults: { hw: 3, hd: 3, h: 1.0, run: 2.2 },
    height(e, x, z) {
      const [u, v] = local(e, x, z);
      const d = Math.max(Math.abs(u) - e.hw, Math.abs(v) - e.hd);
      if (d <= 0) return e.h;
      if (d >= e.run) return 0;
      return e.h * (1 - d / e.run);
    },
  },
  stairs: {                             // platform + steps descending toward +v
    label: 'Stairs',
    defaults: { width: 4.8, h: 0.6, steps: 4, going: 0.6, platDepth: 3.2 },
    height(e, x, z) {
      const [u, v] = local(e, x, z);
      if (Math.abs(u) > e.width / 2) return 0;
      if (v <= 0) return v >= -e.platDepth ? e.h : 0;
      const total = e.steps * e.going;
      if (v >= total) return 0;
      const rise = e.h / e.steps;
      const step = Math.floor(v / e.going);
      return e.h - rise * (step + 1);
    },
  },
  dome: {                               // elliptical pad (grass island, kerbed pad)
    label: 'Island Pad',
    defaults: { rx: 7, rz: 4.5, h: 0.14 },
    height(e, x, z) {
      const c = Math.cos(e.rot || 0), s = Math.sin(e.rot || 0);
      const dx = x - e.x, dz = z - e.z;
      const u = (dx * c + dz * s) / e.rx, v = (-dx * s + dz * c) / e.rz;
      return u * u + v * v < 1 ? e.h : 0;
    },
  },
  bowl: {                               // CARVES negative space. Override, not max.
    label: 'Bowl',
    defaults: { size: 4.2, depth: 1.5 },
    carve: true,
    height(e, x, z) {                   // returns carve value, caller checks inside()
      const [u, v] = local(e, x, z);
      const dw = Math.min(e.size - Math.abs(u), e.size - Math.abs(v));
      return -e.depth + tranny(Math.min(dw, e.depth), e.depth);
    },
    inside(e, x, z) {
      const [u, v] = local(e, x, z);
      return Math.abs(u) < e.size && Math.abs(v) < e.size;
    },
  },
};

// ---------------------------------------------------------------- evaluation
export function elementHeight(e, x, z) {
  const k = ELEMENT_KINDS[e.kind];
  return k ? k.height(e, x, z) : 0;
}

// makeHeightAt(park) -> heightAt(x,z). Closure over the data; rebuild-free (data is live).
export function makeHeightAt(park) {
  return function heightAt(x, z) {
    const B = park.bounds;
    const inPark = x >= B.x0 && x <= B.x1 && z >= B.z0 && z <= B.z1;
    if (!inPark) {                       // parkland grass rising gently away
      const dx = Math.max(B.x0 - x, x - B.x1, 0);
      const dz = Math.max(B.z0 - z, z - B.z1, 0);
      return 0.25 + 0.09 * Math.hypot(dx, dz);
    }
    let h = 0;
    for (const e of park.elements) {
      const k = ELEMENT_KINDS[e.kind];
      if (!k) continue;
      if (k.carve) {
        if (k.inside(e, x, z)) return k.height(e, x, z);   // bowls own their footprint
        continue;
      }
      const eh = k.height(e, x, z);
      if (eh > h) h = eh;
    }
    return h;
  };
}

export function makeNormalAt(heightAt) {
  return function normalAt(x, z, out) {
    const e = 0.18;
    const hx = heightAt(x + e, z) - heightAt(x - e, z);
    const hz = heightAt(x, z + e) - heightAt(x, z - e);
    out.set(-hx, 2 * e, -hz).normalize();
    return out;
  };
}

// footprint hit-test for the editor (generous margins so small things stay clickable)
export function elementHit(e, x, z) {
  const M = 0.4;
  const k = ELEMENT_KINDS[e.kind];
  if (!k) return false;
  switch (e.kind) {
    case 'quarter': { const [u, v] = local(e, x, z);
      return Math.abs(u) <= e.len / 2 + M && v >= -e.deck - M && v <= Math.max(e.r0, e.r1) + M; }
    case 'bank': { const [u, v] = local(e, x, z);
      return Math.abs(u) <= e.len / 2 + M && v >= -e.deck - M && v <= e.run + M; }
    case 'funbox': case 'pyramid': { const [u, v] = local(e, x, z);
      const sk = e.skirt ?? e.run;
      return Math.abs(u) <= e.hw + sk + M && Math.abs(v) <= e.hd + sk + M; }
    case 'ledge': { const [u, v] = local(e, x, z);
      return Math.abs(u) <= e.hw + M && Math.abs(v) <= e.hd + M; }
    case 'mogul': return Math.hypot(x - e.x, z - e.z) <= e.s + M;
    case 'spine': { const [u, v] = local(e, x, z);
      return Math.abs(u) <= e.len / 2 + M && Math.abs(v) <= e.r + M; }
    case 'stairs': { const [u, v] = local(e, x, z);
      return Math.abs(u) <= e.width / 2 + M && v >= -e.platDepth - M && v <= e.steps * e.going + M; }
    case 'dome': { const c = Math.cos(e.rot || 0), s = Math.sin(e.rot || 0);
      const dx = x - e.x, dz = z - e.z;
      const u = (dx * c + dz * s) / (e.rx + M), v = (-dx * s + dz * c) / (e.rz + M);
      return u * u + v * v < 1; }
    case 'bowl': { const [u, v] = local(e, x, z);
      return Math.abs(u) <= e.size + M && Math.abs(v) <= e.size + M; }
  }
  return false;
}

// footprint outline (world-space [x,z] loop) for selection highlights
export function elementOutline(e) {
  const rot = e.rot || 0, c = Math.cos(rot), s = Math.sin(rot);
  const W = (u, v) => [e.x + u * c - v * s, e.z + u * s + v * c];
  const rect = (u0, u1, v0, v1) => [W(u0, v0), W(u1, v0), W(u1, v1), W(u0, v1)];
  switch (e.kind) {
    case 'quarter': return rect(-e.len / 2, e.len / 2, -e.deck, Math.max(e.r0, e.r1));
    case 'bank': return rect(-e.len / 2, e.len / 2, -e.deck, e.run);
    case 'funbox': return rect(-e.hw - e.skirt, e.hw + e.skirt, -e.hd - e.skirt, e.hd + e.skirt);
    case 'pyramid': return rect(-e.hw - e.run, e.hw + e.run, -e.hd - e.run, e.hd + e.run);
    case 'ledge': return rect(-e.hw, e.hw, -e.hd, e.hd);
    case 'mogul': { const pts = []; for (let i = 0; i < 24; i++) {
      const a = i / 24 * Math.PI * 2; pts.push([e.x + Math.cos(a) * e.s, e.z + Math.sin(a) * e.s]); }
      return pts; }
    case 'spine': return rect(-e.len / 2, e.len / 2, -e.r, e.r);
    case 'stairs': return rect(-e.width / 2, e.width / 2, -e.platDepth, e.steps * e.going);
    case 'dome': { const pts = []; for (let i = 0; i < 24; i++) {
      const a = i / 24 * Math.PI * 2;
      pts.push(W(Math.cos(a) * e.rx, Math.sin(a) * e.rz)); }
      return pts; }
    case 'bowl': return rect(-e.size, e.size, -e.size, e.size);
  }
  return [];
}

// ---------------------------------------------------------------- park scaffolding
let idCounter = 1;
export const newId = () => 'e' + (idCounter++) + '_' + ((Math.random() * 1e6) | 0).toString(36);

export function newElement(kind, x, z) {
  const k = ELEMENT_KINDS[kind];
  return { id: newId(), kind, x: +x.toFixed(2), z: +z.toFixed(2), rot: 0,
           ...structuredClone(k.defaults) };
}

export function emptyPark(name = 'NEW PARK') {
  return {
    name,
    bounds: { x0: -30, x1: 30, z0: -20, z1: 20 },
    slabColor: '#7fae6f',
    grassColor: '#4d7c3c',
    spawn: { x: -20, z: -12, heading: 0.8 },
    elements: [], rails: [], gaps: [], letters: [], zones: [], decals: [], props: [],
  };
}