Modulation Curves

Modulation signals run through a response curve between the source and the output range. The curve is a piecewise function from [0, 1] to [0, 1], built from control points with optional Bezier tangent handles. Lightbridge ships 16 presets to cover common shapes — you can also build fully custom curves from inside the modulation panel.

Every preview below is computed at build time from the same evaluation function the engine uses at runtime (evaluateCurve in packages/engine/src/modulation/EnvelopeCurve.ts). They are exact.

Linear & inverse

The identity pair. linear passes the signal through unchanged; inverse flips it end-for-end.

Linear

Identity mapping — input passes through unchanged.

Inverse

Straight diagonal, flipped — 1 → 0 and 0 → 1.

Eases

The classic animation curves. Use these when the default linear response feels lifeless.

Ease In accelerates — useful for “hit hard at the end” behaviours.
Ease Out decelerates — gentler responses on big signals.
S-Curve combines both — a smoothstep that flattens the ends and steepens the middle.

Ease In

Slow start, fast finish — cubic ease in.

Ease Out

Fast start, slow finish — cubic ease out.

S-Curve

Slow, fast, slow — smoothstep / cubic S-curve.

Thresholds & stairs

Hard discrete responses. step is binary. 4-Step Ladder quantises into four plateaus, 8-Step Ladder into eight. Use these to turn a smooth signal into chunky, pixel-art-like motion.

Step

Hard threshold at the midpoint.

4-Step Ladder

Four equal steps from 0 to 1.

8-Step Ladder

Eight finer steps — quantises the signal harder.

Bounce & pulse

Shapes that peak and return. bounce overshoots and settles — great for “punchy” reactions. pulse and gate give you rectangular on/off windows with soft and hard edges respectively.

Bounce

Overshoot past the target, then settle — smooth bounce.

Pulse

Smooth rectangular pulse — ramps up, holds, ramps down.

Gate

Hard rectangular gate — on/off at fixed thresholds.

Shaped peaks

Single-peak shapes. bell is smooth and symmetrical. spike is the same idea but angular. notch is the inverse of spike — a flat signal with a sharp dip.

Bell

Smooth dome — peaks in the middle, falls off gently.

Spike

Sharp triangular peak — sudden hit, sudden fall.

Notch

Inverted spike — flat with a sharp dip at the middle.

Plateau & alternating

shelf is a flat hold zone with smooth ramps into and out — useful for “hold at 80%” behaviours. zigzag gives you two alternating peaks across the input, which produces interesting rhythmic behaviour when driven by a slow LFO.

Shelf

Plateau with smooth ramps into and out of the hold zone.

Zigzag

Sawtooth with alternating peaks and valleys.

Picking a curve

Rough guide:

You want…	Try…
The modulation to feel linear and natural	`linear` (default)
A “dead zone” at low signal and snap at high	`easeIn`, `step`
Instant reaction that settles	`easeOut`
Smooth build-up and release	`sCurve`, `bell`
On/off with hard edges	`gate`
On/off with soft edges	`pulse`
Overshoot and settle (physics feel)	`bounce`
Chunky discrete levels	`stairs4`, `stairs8`
Flat but with a dip	`notch`
Flat plateau with edges	`shelf`
Rhythmic alternating shape	`zigzag`

Custom curves

The modulation panel lets you edit the curve directly — add a point by clicking the curve, drag handles to adjust Bezier tangents, right-click for a context menu of operations. Custom curves are persisted per slot in the show file.

If you build a curve you want to reuse, the mod preset system saves the curve shape (without the rest of the slot config) so you can apply the same shape to other parameters later.

The Modulation System — where curves sit in the signal flow.
Beat Sync guide — practical uses for curves on beat-synced modulation.
Audio Reactivity guide — practical uses for curves on audio-reactive modulation.