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Documentation / @debuffjp/core / SpatialHash

Class: SpatialHash<T> ​

Defined in: core/src/spatial.ts:32

A uniform grid for "what's near this" queries: enemies near the player, shots against a crowd, a swarm keeping its members apart. Put items in with rebuild(items) once per step (or clear and insert), then ask near or nearest, which only look at the cells around the point instead of every item.

Pick a cell size about the radius you query most. Results come in a fixed order (cells row by row, items in insertion order), so replays and tests stay deterministic. After the first few steps it allocates nothing: cell arrays are reused, and cells that empty out are released. Items are points: for big objects, query with the radius plus their size. Don't insert or rebuild while a query is running; nested queries are fine.

ts
const grid = new SpatialHash<Enemy>(24);
// in update, after moving:
grid.rebuild(enemies);
grid.near(shot.x, shot.y, 12, (e) => {
  hit(e);
  return true; // stop at the first
});
const target = grid.nearest(player.x, player.y, 200, (e) => !e.dead);

Type Parameters ​

T ​

T extends Point

Constructors ​

Constructor ​

new SpatialHash<T>(cellSize?): SpatialHash<T>

Defined in: core/src/spatial.ts:38

Parameters ​

cellSize? ​

number = 32

Returns ​

SpatialHash<T>

Properties ​

cellSize ​

readonly cellSize: number

Defined in: core/src/spatial.ts:33

Accessors ​

size ​

Get Signature ​

get size(): number

Defined in: core/src/spatial.ts:45

How many items are in the grid.

Returns ​

number

Methods ​

clear() ​

clear(): void

Defined in: core/src/spatial.ts:54

Empty the grid, keeping its arrays for the next fill. Cells keep their place in the map from one fill to the next (most are refilled, and re-adding them was a third slower); a cell that stayed empty for a whole fill is released, so a world explored over time doesn't keep growing the grid.

Returns ​

void

insert() ​

insert(item): void

Defined in: core/src/spatial.ts:65

Add one item at its current position. Moving it later doesn't move it in the grid: rebuild each step.

Parameters ​

item ​

T

Returns ​

void

near() ​

near(x, y, radius, visit): boolean

Defined in: core/src/spatial.ts:86

Call visit for every item within radius of (x, y), measured centre to centre. Return true from visit to stop. Returns true if it was stopped.

Parameters ​

x ​

number

y ​

number

radius ​

number

visit ​

(item, distanceSquared) => boolean | undefined

Returns ​

boolean

nearest() ​

nearest(x, y, radius, accept?): T | undefined

Defined in: core/src/spatial.ts:107

The item closest to (x, y) within radius that accept allows (default: any). Ties go to the first found.

Parameters ​

x ​

number

y ​

number

radius ​

number

accept? ​

(item) => boolean

Returns ​

T | undefined

rebuild() ​

rebuild(items): void

Defined in: core/src/spatial.ts:77

clear(), then insert every item. Call it once per step after things have moved.

Parameters ​

items ​

Iterable<T>

Returns ​

void