| 1 | import type { Tile } from '../game/tiles'; |
| 2 | import type { SeatId } from '../game/types'; |
| 3 | |
| 4 | /** |
| 5 | * The tiles in the middle of the table, as things with weight. |
| 6 | * |
| 7 | * Pure and deterministic: no DOM, no clock, no randomness. Where the world's |
| 8 | * measurements come from is `geometry.ts`; what gets thrown into it and when is |
| 9 | * `pool.ts`; drawing it is `ui/Pool.tsx`. Anything random — the spread on a |
| 10 | * placed tile, the scatter a reloaded pile is rebuilt from — is decided by the |
| 11 | * caller and arrives as a spawn impulse, which is what lets the same hand come |
| 12 | * back to the same pile after a refresh. |
| 13 | * |
| 14 | * Everything is in CSS pixels, table-local, and seconds. |
| 15 | */ |
| 16 | |
| 17 | /** One fixed step. Small enough that a hard flick can't tunnel a wall. */ |
| 18 | export const FIXED_DT = 1 / 120; |
| 19 | /** |
| 20 | * Most catch-up a single frame will simulate. A tab that was in the background |
| 21 | * for a minute comes back to a settled pile, not to a spin through 7200 steps. |
| 22 | */ |
| 23 | const MAX_SUBSTEPS = 8; |
| 24 | |
| 25 | /** Falls onto the felt in about half a second from a normal throw. */ |
| 26 | const GRAVITY = 2600; |
| 27 | /** Tiles are dense and land flat; they do not bounce much. */ |
| 28 | const Z_RESTITUTION = 0.34; |
| 29 | /** Below this the tile is flat on the felt: sliding, and in the way of others. */ |
| 30 | const ON_FELT = 8; |
| 31 | /** |
| 32 | * How high a standing stack of two reaches. A tile still above this sails over |
| 33 | * the wall — which is exactly what a *placed* tile does, and what a thrown one |
| 34 | * must not need to do. |
| 35 | */ |
| 36 | export const WALL_HEIGHT = 30; |
| 37 | |
| 38 | /** Felt friction: an exponential part that kills speed, and a constant part |
| 39 | * that actually brings it to a stop rather than to an asymptote. */ |
| 40 | const FELT_DAMP = 4.2; |
| 41 | const FELT_STOP = 90; |
| 42 | const SPIN_DAMP = 5; |
| 43 | const SPIN_STOP = 1.2; |
| 44 | |
| 45 | const BOUND_RESTITUTION = 0.42; |
| 46 | const BOUND_FRICTION = 0.86; |
| 47 | const TILE_RESTITUTION = 0.4; |
| 48 | |
| 49 | /** Asleep after this many consecutive steps of going nowhere. */ |
| 50 | const SLEEP_SPEED = 7; |
| 51 | const SLEEP_SPIN = 0.2; |
| 52 | const SLEEP_STEPS = 10; |
| 53 | /** |
| 54 | * Overlap small enough to live with. Without this a crowded pool never sleeps: |
| 55 | * a tile squeezed between its neighbours and the pool's edge gets pushed out of |
| 56 | * contact and clamped back into it on every step, for ever, and each of those |
| 57 | * counts as being disturbed. Tolerating a fraction of a pixel costs nothing to |
| 58 | * look at and is what lets the pile go quiet. |
| 59 | */ |
| 60 | const CONTACT_SLOP = 0.5; |
| 61 | /** |
| 62 | * A body moving this slowly for this long is put to sleep whatever it thinks it |
| 63 | * is doing. The backstop that guarantees the pile always settles — counted from |
| 64 | * when it last woke, not from when it was thrown. |
| 65 | */ |
| 66 | const AWAKE_LIMIT = 600; |
| 67 | |
| 68 | /** Pulls a tile that landed short of the pool in towards the rest of them. */ |
| 69 | const ENTRY_PULL = 700; |
| 70 | /** |
| 71 | * How long a tile gets to find its own way into the pool before it is simply |
| 72 | * put there. A discard is game state made visible — it has to be in the middle |
| 73 | * where it can be seen and counted — so a tile that has got itself wedged |
| 74 | * against a standing stack, or is bouncing between two of them, cannot be left |
| 75 | * out there. Two seconds is far longer than any real throw takes to settle. |
| 76 | */ |
| 77 | const ENTRY_GRACE = 240; |
| 78 | |
| 79 | /** Quietest impact worth a sound, as a fraction of a hard landing. */ |
| 80 | const IMPACT_FLOOR = 0.12; |
| 81 | |
| 82 | export interface Rect { |
| 83 | x: number; |
| 84 | y: number; |
| 85 | w: number; |
| 86 | h: number; |
| 87 | } |
| 88 | |
| 89 | export interface Body { |
| 90 | tile: Tile; |
| 91 | /** Who threw it — for the fly-out when it is claimed, not for any marking. */ |
| 92 | seat: SeatId; |
| 93 | /** Centre on the felt plane. */ |
| 94 | x: number; |
| 95 | y: number; |
| 96 | vx: number; |
| 97 | vy: number; |
| 98 | /** Height above the felt, and its rate. Only ever >= 0. */ |
| 99 | z: number; |
| 100 | vz: number; |
| 101 | angle: number; |
| 102 | spin: number; |
| 103 | w: number; |
| 104 | h: number; |
| 105 | /** |
| 106 | * Whether it has ever been inside the pool. Until it has, it is free to fly |
| 107 | * over the wall from a seat's edge; once it has, the pool keeps it. |
| 108 | */ |
| 109 | entered: boolean; |
| 110 | resting: boolean; |
| 111 | /** Consecutive slow steps, counting towards sleep. */ |
| 112 | still: number; |
| 113 | /** Steps lived, for the grace period on getting into the pool. */ |
| 114 | age: number; |
| 115 | /** Steps since it last woke, for the backstop on settling. */ |
| 116 | awake: number; |
| 117 | } |
| 118 | |
| 119 | /** A collision loud enough to hear. `strength` is 0..1. */ |
| 120 | export interface Impact { |
| 121 | x: number; |
| 122 | y: number; |
| 123 | strength: number; |
| 124 | } |
| 125 | |
| 126 | export interface World { |
| 127 | /** Where tiles come to rest — inside the wall square. */ |
| 128 | bounds: Rect; |
| 129 | /** Stacks of two still standing. Half and spent stacks are not obstacles. */ |
| 130 | walls: Rect[]; |
| 131 | bodies: Body[]; |
| 132 | /** Left-over time from the last frame, so steps stay a fixed size. */ |
| 133 | carry: number; |
| 134 | } |
| 135 | |
| 136 | export interface Spawn { |
| 137 | tile: Tile; |
| 138 | seat: SeatId; |
| 139 | x: number; |
| 140 | y: number; |
| 141 | vx: number; |
| 142 | vy: number; |
| 143 | z: number; |
| 144 | vz: number; |
| 145 | angle: number; |
| 146 | spin: number; |
| 147 | w: number; |
| 148 | h: number; |
| 149 | /** Already settled — a pile being rebuilt after a reload or an undo. */ |
| 150 | atRest?: boolean; |
| 151 | } |
| 152 | |
| 153 | export function createWorld(bounds: Rect, walls: Rect[] = []): World { |
| 154 | return { bounds, walls, bodies: [], carry: 0 }; |
| 155 | } |
| 156 | |
| 157 | export function addBody(world: World, s: Spawn): Body { |
| 158 | const body: Body = { |
| 159 | tile: s.tile, |
| 160 | seat: s.seat, |
| 161 | x: s.x, |
| 162 | y: s.y, |
| 163 | vx: s.atRest ? 0 : s.vx, |
| 164 | vy: s.atRest ? 0 : s.vy, |
| 165 | z: s.atRest ? 0 : s.z, |
| 166 | vz: s.atRest ? 0 : s.vz, |
| 167 | angle: s.angle, |
| 168 | spin: s.atRest ? 0 : s.spin, |
| 169 | w: s.w, |
| 170 | h: s.h, |
| 171 | entered: !!s.atRest, |
| 172 | resting: !!s.atRest, |
| 173 | still: s.atRest ? SLEEP_STEPS : 0, |
| 174 | age: 0, |
| 175 | awake: 0, |
| 176 | }; |
| 177 | world.bodies.push(body); |
| 178 | // A tile dropped straight into a settled pile still has to make room. |
| 179 | if (s.atRest) separate(world, body); |
| 180 | return body; |
| 181 | } |
| 182 | |
| 183 | /** Collision radius. A shade under the tile's mean half-extent, so a pool |
| 184 | * overlaps the way a real one does instead of packing like marbles. */ |
| 185 | const radiusOf = (b: Body) => (b.w + b.h) * 0.22; |
| 186 | |
| 187 | const inside = (r: Rect, x: number, y: number) => |
| 188 | x >= r.x && x <= r.x + r.w && y >= r.y && y <= r.y + r.h; |
| 189 | |
| 190 | /** |
| 191 | * Run the world forward. `elapsed` is real seconds since the last call; it is |
| 192 | * consumed in fixed steps so the result does not depend on the frame rate. |
| 193 | * Returns the impacts worth a sound. |
| 194 | */ |
| 195 | export function advance(world: World, elapsed: number): Impact[] { |
| 196 | world.carry += Math.max(0, elapsed); |
| 197 | let steps = Math.floor(world.carry / FIXED_DT); |
| 198 | if (steps > MAX_SUBSTEPS) { |
| 199 | // Drop the backlog rather than working through it. |
| 200 | world.carry = 0; |
| 201 | steps = MAX_SUBSTEPS; |
| 202 | } else { |
| 203 | world.carry -= steps * FIXED_DT; |
| 204 | } |
| 205 | |
| 206 | const impacts: Impact[] = []; |
| 207 | for (let i = 0; i < steps; i++) step(world, impacts); |
| 208 | return impacts; |
| 209 | } |
| 210 | |
| 211 | /** One fixed step. Exported for the tests, which drive it directly. */ |
| 212 | export function step(world: World, impacts: Impact[] = []): Impact[] { |
| 213 | const dt = FIXED_DT; |
| 214 | |
| 215 | for (const b of world.bodies) { |
| 216 | if (b.resting) continue; |
| 217 | b.age++; |
| 218 | b.awake++; |
| 219 | |
| 220 | // --- through the air --- |
| 221 | if (b.z > 0 || b.vz !== 0) { |
| 222 | b.vz -= GRAVITY * dt; |
| 223 | b.z += b.vz * dt; |
| 224 | if (b.z <= 0) { |
| 225 | const landing = Math.abs(b.vz); |
| 226 | b.z = 0; |
| 227 | // Below a knock it stops dead rather than shivering out a bounce. |
| 228 | b.vz = landing > 40 ? landing * Z_RESTITUTION : 0; |
| 229 | const strength = Math.min(1, landing / 900); |
| 230 | if (strength > IMPACT_FLOOR) impacts.push({ x: b.x, y: b.y, strength }); |
| 231 | } |
| 232 | } |
| 233 | |
| 234 | b.x += b.vx * dt; |
| 235 | b.y += b.vy * dt; |
| 236 | b.angle += b.spin * dt; |
| 237 | |
| 238 | if (inside(world.bounds, b.x, b.y)) b.entered = true; |
| 239 | else if (b.age > ENTRY_GRACE) { |
| 240 | // Out of time going the long way round. Put it in, gently. |
| 241 | b.entered = true; |
| 242 | b.z = 0; |
| 243 | b.vz = 0; |
| 244 | clampInto(world.bounds, b); |
| 245 | } |
| 246 | |
| 247 | // --- on the felt --- |
| 248 | if (b.z <= ON_FELT) { |
| 249 | damp(b, dt); |
| 250 | // A tile that fell short skids in rather than sitting outside the pool. |
| 251 | if (!b.entered) pullIn(world, b, dt); |
| 252 | } |
| 253 | |
| 254 | // A tile still above the wall is clear of it. |
| 255 | if (b.z < WALL_HEIGHT) { |
| 256 | for (const wall of world.walls) hitWall(b, wall, impacts); |
| 257 | } |
| 258 | |
| 259 | if (b.entered) keepInBounds(world, b, impacts); |
| 260 | } |
| 261 | |
| 262 | collideTiles(world, impacts); |
| 263 | // Deciding to sleep comes last, so it judges where the step actually left |
| 264 | // things — before, a contact resolved after the decision would undo it and |
| 265 | // a crowded pool would stay awake for ever. |
| 266 | for (const b of world.bodies) if (!b.resting) trySleep(b); |
| 267 | return impacts; |
| 268 | } |
| 269 | |
| 270 | function damp(b: Body, dt: number) { |
| 271 | const k = Math.exp(-FELT_DAMP * dt); |
| 272 | b.vx *= k; |
| 273 | b.vy *= k; |
| 274 | b.spin *= Math.exp(-SPIN_DAMP * dt); |
| 275 | |
| 276 | const speed = Math.hypot(b.vx, b.vy); |
| 277 | if (speed > 0) { |
| 278 | const next = Math.max(0, speed - FELT_STOP * dt); |
| 279 | b.vx = (b.vx / speed) * next; |
| 280 | b.vy = (b.vy / speed) * next; |
| 281 | } |
| 282 | const spin = Math.abs(b.spin); |
| 283 | if (spin > 0) { |
| 284 | const next = Math.max(0, spin - SPIN_STOP * dt); |
| 285 | b.spin = Math.sign(b.spin) * next; |
| 286 | } |
| 287 | } |
| 288 | |
| 289 | /** Nudges a tile that landed outside the pool towards the rest of them. */ |
| 290 | function pullIn(world: World, b: Body, dt: number) { |
| 291 | const cx = world.bounds.x + world.bounds.w / 2; |
| 292 | const cy = world.bounds.y + world.bounds.h / 2; |
| 293 | const dx = cx - b.x; |
| 294 | const dy = cy - b.y; |
| 295 | const d = Math.hypot(dx, dy) || 1; |
| 296 | b.vx += (dx / d) * ENTRY_PULL * dt; |
| 297 | b.vy += (dy / d) * ENTRY_PULL * dt; |
| 298 | } |
| 299 | |
| 300 | /** Bounce off a standing stack. The stacks are axis-aligned, so the shallower |
| 301 | * overlap is the axis to push out along. */ |
| 302 | function hitWall(b: Body, wall: Rect, impacts: Impact[]) { |
| 303 | const r = radiusOf(b); |
| 304 | const left = b.x + r - wall.x; |
| 305 | const right = wall.x + wall.w - (b.x - r); |
| 306 | const top = b.y + r - wall.y; |
| 307 | const bottom = wall.y + wall.h - (b.y - r); |
| 308 | if (left <= 0 || right <= 0 || top <= 0 || bottom <= 0) return; |
| 309 | |
| 310 | const speed = Math.hypot(b.vx, b.vy); |
| 311 | const min = Math.min(left, right, top, bottom); |
| 312 | if (min === left) { |
| 313 | b.x = wall.x - r; |
| 314 | b.vx = -Math.abs(b.vx) * BOUND_RESTITUTION; |
| 315 | } else if (min === right) { |
| 316 | b.x = wall.x + wall.w + r; |
| 317 | b.vx = Math.abs(b.vx) * BOUND_RESTITUTION; |
| 318 | } else if (min === top) { |
| 319 | b.y = wall.y - r; |
| 320 | b.vy = -Math.abs(b.vy) * BOUND_RESTITUTION; |
| 321 | } else { |
| 322 | b.y = wall.y + wall.h + r; |
| 323 | b.vy = Math.abs(b.vy) * BOUND_RESTITUTION; |
| 324 | } |
| 325 | b.spin *= 0.7; |
| 326 | b.resting = false; |
| 327 | b.still = 0; |
| 328 | const strength = Math.min(1, speed / 1100); |
| 329 | if (strength > IMPACT_FLOOR) impacts.push({ x: b.x, y: b.y, strength }); |
| 330 | } |
| 331 | |
| 332 | /** The pool's edge. Once a tile is in, it stays in — this is the invariant the |
| 333 | * tests pin, since a discard that slid off the table would be lost. */ |
| 334 | function keepInBounds(world: World, b: Body, impacts: Impact[]) { |
| 335 | const r = radiusOf(b); |
| 336 | const { x, y, w, h } = world.bounds; |
| 337 | // A pool narrower than a tile would otherwise fight itself; centre instead. |
| 338 | const minX = w <= r * 2 ? x + w / 2 : x + r; |
| 339 | const maxX = w <= r * 2 ? x + w / 2 : x + w - r; |
| 340 | const minY = h <= r * 2 ? y + h / 2 : y + r; |
| 341 | const maxY = h <= r * 2 ? y + h / 2 : y + h - r; |
| 342 | |
| 343 | let hit = 0; |
| 344 | if (b.x < minX) { |
| 345 | b.x = minX; |
| 346 | hit = Math.max(hit, Math.abs(b.vx)); |
| 347 | b.vx = Math.abs(b.vx) * BOUND_RESTITUTION; |
| 348 | b.vy *= BOUND_FRICTION; |
| 349 | } else if (b.x > maxX) { |
| 350 | b.x = maxX; |
| 351 | hit = Math.max(hit, Math.abs(b.vx)); |
| 352 | b.vx = -Math.abs(b.vx) * BOUND_RESTITUTION; |
| 353 | b.vy *= BOUND_FRICTION; |
| 354 | } |
| 355 | if (b.y < minY) { |
| 356 | b.y = minY; |
| 357 | hit = Math.max(hit, Math.abs(b.vy)); |
| 358 | b.vy = Math.abs(b.vy) * BOUND_RESTITUTION; |
| 359 | b.vx *= BOUND_FRICTION; |
| 360 | } else if (b.y > maxY) { |
| 361 | b.y = maxY; |
| 362 | hit = Math.max(hit, Math.abs(b.vy)); |
| 363 | b.vy = -Math.abs(b.vy) * BOUND_RESTITUTION; |
| 364 | b.vx *= BOUND_FRICTION; |
| 365 | } |
| 366 | // Only a real knock counts as being disturbed. A tile held against the edge |
| 367 | // by its neighbours is clamped every single step, and treating that as a |
| 368 | // knock would keep the whole pool awake for ever. |
| 369 | if (hit > SLEEP_SPEED) { |
| 370 | b.still = 0; |
| 371 | const strength = Math.min(1, hit / 1100); |
| 372 | if (strength > IMPACT_FLOOR) impacts.push({ x: b.x, y: b.y, strength }); |
| 373 | } |
| 374 | } |
| 375 | |
| 376 | /** |
| 377 | * Tile against tile, circles rather than rotated rectangles. A mahjong pool is |
| 378 | * a forgiving thing to approximate and tiles are near enough square (1 : 1.375) |
| 379 | * that the difference does not read; rotated-rectangle SAT is a drop-in upgrade |
| 380 | * here if it ever does. |
| 381 | * |
| 382 | * Only tiles flat on the felt take part, so a thrown tile passes over the pile |
| 383 | * instead of shouldering through it, and only awake ones are checked against |
| 384 | * the rest — which is nearly always one tile against a sleeping pile. |
| 385 | */ |
| 386 | function collideTiles(world: World, impacts: Impact[]) { |
| 387 | const bodies = world.bodies; |
| 388 | for (let i = 0; i < bodies.length; i++) { |
| 389 | const a = bodies[i]; |
| 390 | if (a.z > ON_FELT) continue; |
| 391 | for (let j = i + 1; j < bodies.length; j++) { |
| 392 | const b = bodies[j]; |
| 393 | if (b.z > ON_FELT) continue; |
| 394 | // A pile that has settled is left alone until something disturbs it. |
| 395 | if (a.resting && b.resting) continue; |
| 396 | resolvePair(a, b, impacts); |
| 397 | } |
| 398 | } |
| 399 | } |
| 400 | |
| 401 | function resolvePair(a: Body, b: Body, impacts: Impact[]) { |
| 402 | const ra = radiusOf(a); |
| 403 | const rb = radiusOf(b); |
| 404 | const min = ra + rb; |
| 405 | let dx = b.x - a.x; |
| 406 | let dy = b.y - a.y; |
| 407 | let d = Math.hypot(dx, dy); |
| 408 | if (d >= min) return; |
| 409 | // Resting in contact is not a collision. See CONTACT_SLOP. |
| 410 | const overlap = min - d - CONTACT_SLOP; |
| 411 | if (overlap <= 0) return; |
| 412 | |
| 413 | if (d < 0.0001) { |
| 414 | // Exactly on top of each other: pick an axis so they can get apart. |
| 415 | dx = 1; |
| 416 | dy = 0; |
| 417 | d = 1; |
| 418 | } |
| 419 | const nx = dx / d; |
| 420 | const ny = dy / d; |
| 421 | |
| 422 | // Push apart. A tile that has settled is the heavy one: a tile thrown into a |
| 423 | // pool shoulders in, rather than the pool scattering out of its way. |
| 424 | const aShare = a.resting === b.resting ? 0.5 : a.resting ? 0 : 1; |
| 425 | const bShare = 1 - aShare; |
| 426 | a.x -= nx * overlap * aShare; |
| 427 | a.y -= ny * overlap * aShare; |
| 428 | b.x += nx * overlap * bShare; |
| 429 | b.y += ny * overlap * bShare; |
| 430 | |
| 431 | // Impulse along the centre line, plus a spin kick off what is left over. |
| 432 | // |
| 433 | // Only a genuine approach speed counts, and only that wakes anything. Nudging |
| 434 | // two touching tiles apart is not a collision: a jammed corner of the pool is |
| 435 | // corrected by a fraction of a pixel every step for as long as it is jammed, |
| 436 | // and treating each of those as a shove would keep the pile awake for ever. |
| 437 | const rvx = b.vx - a.vx; |
| 438 | const rvy = b.vy - a.vy; |
| 439 | const along = rvx * nx + rvy * ny; |
| 440 | if (along >= -SLEEP_SPEED) return; |
| 441 | |
| 442 | const jolt = -along * (1 + TILE_RESTITUTION) * 0.5; |
| 443 | a.vx -= nx * jolt; |
| 444 | a.vy -= ny * jolt; |
| 445 | b.vx += nx * jolt; |
| 446 | b.vy += ny * jolt; |
| 447 | |
| 448 | const tangent = rvx * -ny + rvy * nx; |
| 449 | a.spin -= tangent * 0.004; |
| 450 | b.spin += tangent * 0.004; |
| 451 | |
| 452 | const strength = Math.min(1, Math.abs(along) / 900); |
| 453 | if (strength > IMPACT_FLOOR) impacts.push({ x: b.x, y: b.y, strength }); |
| 454 | |
| 455 | // Whatever was asleep has been shoved, so it is awake now. |
| 456 | wake(a); |
| 457 | wake(b); |
| 458 | } |
| 459 | |
| 460 | function wake(b: Body) { |
| 461 | if (b.resting) b.awake = 0; |
| 462 | b.resting = false; |
| 463 | b.still = 0; |
| 464 | } |
| 465 | |
| 466 | function sleep(b: Body) { |
| 467 | b.vx = 0; |
| 468 | b.vy = 0; |
| 469 | b.spin = 0; |
| 470 | b.z = 0; |
| 471 | b.vz = 0; |
| 472 | b.resting = true; |
| 473 | b.awake = 0; |
| 474 | } |
| 475 | |
| 476 | function trySleep(b: Body) { |
| 477 | const speed = Math.hypot(b.vx, b.vy); |
| 478 | const slow = b.entered && b.z <= 0 && b.vz === 0 && speed < SLEEP_SPEED && Math.abs(b.spin) < SLEEP_SPIN; |
| 479 | if (slow && ++b.still >= SLEEP_STEPS) return sleep(b); |
| 480 | if (!slow) b.still = 0; |
| 481 | // Backstop: shuffling about in a crowded pool for this long is settled enough. |
| 482 | if (b.entered && b.awake > AWAKE_LIMIT && speed < SLEEP_SPEED * 4) sleep(b); |
| 483 | } |
| 484 | |
| 485 | /** |
| 486 | * Make room for a tile placed straight into a settled pile, without running |
| 487 | * time. Used when a pile is rebuilt — a reload, an undo — where the tiles have |
| 488 | * to be somewhere sensible immediately and nothing should appear to move. |
| 489 | */ |
| 490 | function separate(world: World, body: Body, passes = 12) { |
| 491 | // Which way to go when two tiles are exactly on top of each other. Stepping |
| 492 | // by the golden angle fans successive tiles out in every direction, where a |
| 493 | // fixed axis would march them all one way and pack them against a pool edge. |
| 494 | const escapeAngle = world.bodies.indexOf(body) * 2.39996; |
| 495 | |
| 496 | for (let p = 0; p < passes; p++) { |
| 497 | let moved = false; |
| 498 | for (const other of world.bodies) { |
| 499 | if (other === body) continue; |
| 500 | const min = radiusOf(body) + radiusOf(other); |
| 501 | let dx = body.x - other.x; |
| 502 | let dy = body.y - other.y; |
| 503 | let d = Math.hypot(dx, dy); |
| 504 | if (d >= min) continue; |
| 505 | if (d < 0.0001) { |
| 506 | dx = Math.cos(escapeAngle + p); |
| 507 | dy = Math.sin(escapeAngle + p); |
| 508 | d = 1; |
| 509 | } |
| 510 | body.x = other.x + (dx / d) * min; |
| 511 | body.y = other.y + (dy / d) * min; |
| 512 | moved = true; |
| 513 | } |
| 514 | clampInto(world.bounds, body); |
| 515 | if (!moved) break; |
| 516 | } |
| 517 | } |
| 518 | |
| 519 | function clampInto(r: Rect, b: Body) { |
| 520 | const rad = radiusOf(b); |
| 521 | const minX = r.w <= rad * 2 ? r.x + r.w / 2 : r.x + rad; |
| 522 | const maxX = r.w <= rad * 2 ? r.x + r.w / 2 : r.x + r.w - rad; |
| 523 | const minY = r.h <= rad * 2 ? r.y + r.h / 2 : r.y + rad; |
| 524 | const maxY = r.h <= rad * 2 ? r.y + r.h / 2 : r.y + r.h - rad; |
| 525 | b.x = Math.min(maxX, Math.max(minX, b.x)); |
| 526 | b.y = Math.min(maxY, Math.max(minY, b.y)); |
| 527 | } |
| 528 | |
| 529 | /** Whether everything has settled — what the render loop idles on. */ |
| 530 | export const settled = (world: World) => world.bodies.every((b) => b.resting); |
| 531 | |
| 532 | /** Scale a tile is drawn at, given how high it is. Sells the arc on a flat |
| 533 | * canvas; the renderer offsets the shadow by the same height. */ |
| 534 | export const zScale = (z: number) => 1 + z * 0.0016; |