Program and Scene

createProgram

createProgram wraps an async build callback and returns IntermactProgram. IntermactCanvas or buildProgram runs the build once, producing Player + Storyboard.

import { createProgram, xy } from "@intermact/core";

const program = createProgram(async (ctx) => {
  const scene = ctx.createScene2D({
    coordinate: "cartesian", // or "polar"
    domain: { x: [-5, 5], y: [-4, 4] },
    fit: "contain",          // contain | cover | stretch
    background: "#0b1020",
  });
  ctx.mount(scene, ctx.createCamera2D(scene));

  // … register objects, scene.play(…)
});

IntermactProgramContext

Method	Description
createScene2D(props)	Create Scene2D, bound to ReactiveEngine
createCamera2D(scene, props?)	2D orthographic camera description
mount(scene, camera, rect?)	Record viewport (v0.1 single main scene)
rng	Seeded RNG (createRng); same seed is reproducible

buildProgram(program, { seed }) can run headlessly in Node for tests and export pipelines.

Scene2D

register

Register an immutable IMObject2D into the scene:

const obj = scene.register(circle({ radius: 1, style: { stroke: "#fff" } }), {
  position: xy(1, 2),
  rotation: 0,
  scale: xy(1, 1),
  opacity: 1,
});

register returns RegisteredObject2D — the receiver for all animation APIs.

play

await scene.play(
  obj.create({ duration: 1 }),
  other.fadeIn({ duration: 0.5 }),
);

Multiple Animation arguments play in parallel. Internally compiled into Storyboard tracks — no wall-clock wait.

getAxes

Axes are ordinary registered objects, not special side-effect APIs on Scene:

const axes = scene.getAxes({
  x: [-4, 4],
  y: [-3, 3],
  style: { stroke: "#94a3b8", lineWidth: 0.03 },
  xLabel: "x",
  yLabel: "y",
  showTicks: true,
  showTickLabels: false,
});

await scene.play(axes.fadeIn({ duration: 0.6 }));

axes.handle provides c2p / p2c coordinate mapping (for math construct alignment).

RegisteredObject2D animation shortcuts

Method	Description
create(opts?)	Stroke reveal + optional fill strategy
fadeIn / fadeOut	Opacity tween
moveTo / rotateTo / scaleTo	Transform tweens
fadeTo	Opacity to target value
tween(property, to, opts?)	Generic property tween (including reveal)
addUpdater(fn)	Per-frame update callback (requires scene-bound ReactiveEngine)

See Animation.

Coordinate helpers

import { xy, uv } from "@intermact/core";

xy(1, 2);   // Scene absolute coordinates (same units as domain)
uv(0.5, 0); // Relative UV (layout milestone extension)

scene.coordinateTransform provides absToRel / relToAbs / toPolar / fromPolar (see Coordinates).

Related examples

• timeline/seek-basics — single tween seek
• coords/cartesian-axes — getAxes + fadeIn
• l1/basic-2d — §19.1 comprehensive narrative