Gotchas

Write floats as floats

API functions take floats, and Rhai does not convert integers. point(1, 0) fails with Function not found: point (i64, i64). Write point(1.0, 0.0), and convert loop indices with .to_float():

for i in 0..5 {
    scene.add(dot(point(i.to_float(), 0.0)));
}

Axes ranges are the exception: axes([-3, 3], [-1, 1]) accepts integers.

Add before animating

Animations take the handle scene.add returns, not the shape. Animating something that was never added, or was removed, fails with not in the scene.

Shapes vs. texts

scene.get, scene.always, transform and replacement_transform need shapes. Texts are many glyphs; change them with transform_diff.

Closures run later

Closures passed to always, update, apply_function, function_graph and plot are called during baking, not where they are written. Errors in them are reported at the next scene.play. They cannot use scene; see updaters.

The standard library

Rhai’s standard library is available: sin, cos, min, max, abs, sqrt, to_float, len, map, filter, print and so on. See the Rhai book.

Limits

A script that runs too long or recurses too deep fails rather than hanging: it gets 10 million operations and 64 call levels.