Struct SceneStepper 

pub struct SceneStepper {
    physics_debt: f32,
    audio_debt: f64,
    physics_period: f32,
    sample_period: Option<f64>,
}

The pacing a host uses to step a scene’s worlds frame by frame.

The frame’s own duration is what drives the worlds, and none of their rates is an integer multiple of the display’s, so each frame carries the fraction of a step it did not spend into the next one. Counting seconds rather than frames is what keeps the simulation at its rates on a display that redraws at anything but 60 Hz; a fixed-rate run passes an exact step instead of a measured one, which is what makes it reproducible.

Fields

physics_debt: f32

The physics time the last frame did not spend.

audio_debt: f64

The audio time the last frame did not spend.

physics_period: f32

How long one physics step lasts.

sample_period: Option<f64>

How long one audio frame lasts, or none when the host pulls no audio.

Implementations

impl SceneStepper

pub fn new(physics_hz: f64, sample_rate: Option<u32>) -> Self

A stepper for a scene whose physics world runs at physics_hz, and — when sample_rate is given — whose synthesizer runs at that rate.

Gameplay has no rate here: its world ticks once per frame, with the frame’s own duration.

pub fn step(&mut self, host: &World, worlds: &SceneHandles, delta_seconds: f64)

Step the scene once for delta_seconds: gameplay ticks, physics steps as its rate comes due, and the audio world drains the note jobs those ticks sent.

The render world is not stepped here: it is a sub-world the draw drains, not one with a rate of its own.

pub fn audio_frames(&mut self, delta_seconds: f64) -> usize

The audio frames this frame’s duration asks for, carrying the fraction it did not spend into the next frame.

Zero when the stepper was built without a sample rate.