transform

Import from @pierre/ecs/modules/transform.

Canonical 2D transform primitives: position, velocity, rotation, scale.

API

interface Position { x: number; y: number }
interface Velocity { vx: number; vy: number }
interface Rotation { angle: number }  // radians
interface Scale    { x: number; y: number }  // multiplier per axis

const PositionDef:    ComponentDef<Position>;
const VelocityDef:    ComponentDef<Velocity>;
const RotationDef:    ComponentDef<Rotation>;
const ScaleDef: ComponentDef<Scale>;

ScaleDef is a geometric transform sibling to position/rotation. modules/render-canvas2d reads it when drawing; non-render systems (physics, AI vision) may read it if they need per-entity scaling. Entities without the component render at 1:1.

Data-only module. No systems. A velocity integrator ships separately in @pierre/ecs/modules/motion so games that only need static positions don’t carry motion logic. VelocityDef is the data; only the integrator lives in motion. Whether the velocity data itself belongs here or in motion is unsettled — if it moves, it moves for both transform and transform-3d in one pass so the two dimensions stay aligned.

Usage

import { PositionDef, VelocityDef } from '@pierre/ecs/modules/transform';

world.registerComponent(PositionDef);
world.registerComponent(VelocityDef);

const id = world.spawn({ name: 'blob' });
world.getStore(PositionDef).set(id, { x: 0, y: 0 });
world.getStore(VelocityDef).set(id, { vx: 1, vy: 0 });

Scope

2D only. angle is a scalar in radians (no quaternions). For 3D, the sibling @pierre/ecs/modules/transform-3d ships Position3D ({x,y,z}), Velocity3D, a quaternion Rotation3D, and Scale3D. See docs/plans/ecs-2d-engine-modules.md for the parallel-module strategy.

Anchor convention: position is the entity’s world-space origin. Shape components (ShapeAabbDef, ShapeCircleDef from @pierre/ecs/modules/collision) interpret it per-shape; for AABB the position is the top-left corner, for circle the center.