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Scripts

A script is a JavaScript file that edits a project through Lumit’s own commands. Running one, and what After Effects scripts can do, is in Scripts.

Your first script

Section titled “Your first script”

stripes.js makes a composition of five coloured stripes that fade in one after another:

const comp = lumit.comp.new({
  name: "Stripes",
  width: 1280,
  height: 720,
  frame_rate: 30,
});
const colours = [
  [0.9, 0.3, 0.2],
  [0.9, 0.6, 0.2],
  [0.3, 0.7, 0.4],
  [0.2, 0.5, 0.9],
  [0.5, 0.3, 0.8],
];
colours.forEach((colour, n) => {
  const stripe = lumit.layer.add({
    comp: comp.id,
    kind: "solid",
    name: "Stripe " + (n + 1),
    colour,
    width: 256,
  });
  lumit.layer.keys({
    comp: comp.id,
    layer: stripe.id,
    property: "position",
    value: [128 + 256 * n, 360],
  });
  lumit.layer.keys({
    comp: comp.id,
    layer: stripe.id,
    property: "opacity",
    keys: [
      { time: n * 6, value: 0 },
      { time: n * 6 + 12, value: 100 },
    ],
  });
});
print("Made", colours.length, "stripes");
lumit.comp.frame({ comp: comp.id, time: 18, out: "stripes.png" });

1. Save it as stripes.js in the Scripts folder.

2. Choose File ▸ Scripts ▸ stripes.js. The whole run is one undo step.

3. Or run it from the command line, with no window:

lumit-cli run stripes.js --save-as stripes.lum

The project is saved as stripes.lum. In Lumit, a relative path such as stripes.png is read from the script’s folder. From the command line, it is read from the folder the command runs in.

The lumit object

Section titled “The lumit object”

Every command in the Scripting reference is a method of lumit: layer.add is lumit.layer.add({ ... }). Each takes one object of arguments and answers an object.

NameWhat it is
lumit.command(name, args)Runs a command by its name, as lumit.command("layer.add", { ... }).
lumit.argsThe --arg values from the command line, and an event script’s event and file.
lumit.chooseFile(title, extensions)Opens the system file dialogue and answers the path, or null. On the command line, null.
lumit.readText(path), lumit.readJson(path)Reads a file the script may read.
lumit.frameAt(seconds, comp)The frame of a comp nearest a time in seconds.
print(...), console.log(...)Writes a line to the log, or to standard error on the command line.

A command that fails throws an Error with the reason. A script that does not catch it stops, and the project is left as it was. Undo and redo are not methods: a run is one step.

The value of the script’s last line is its answer. The command line prints it as JSON.

Effects

Section titled “Effects”

effect.add takes Lumit’s name for an effect, its id, or After Effects’ match name. It also takes the effects an extension carries, by name.

effect.get answers one effect with every row it has, including the rows an LFX effect’s or a Custom shader’s Params declare. effect.set sets a row by its id or its label:

const at = { comp: "Stripes", layer: "Stripe 1" };
lumit.effect.add({ ...at, effect: "Blinds" });
lumit.effect.set({ ...at, effect: "Blinds", param: "Spacing", value: 10 });
lumit.effect.get({ ...at, effect: 0 }).params;

Blinds is the first example in LFX effects.

Sharing a script

Section titled “Sharing a script”

A script is one file. Put it in the Scripts folder, or a folder inside it for a submenu of its own. A script reads files with lumit.readText from its own folder and the folders inside it.

Section titled “Related”