aego/engine/res/docs/curves.md

id, icon, group, title, order

id	icon	group	title	order
curves	vec.angular	gameplay	Curves	4

Curves

A curve maps time to a value. Component fields of type curve.Curve describe falloffs, speed ramps and fades; a tween can follow a curve instead of an easing.

---

id: curves/shape icon: code.hints parent: curves order: 1 title: Presets and keys

Presets and keys

A curve is either a preset or a list of keys.

• Preset. An easing on time 0..1: linear and the in/out/inOut family of quad, cubic, sine, expo, back, elastic and bounce.
• Keys. Each key has a time, a value, two slopes, a segment mode and a tangent mode.

Segment	From this key to the next
Bezier	smooth, shaped by the slopes
Linear	a straight line
Step	holds this key's value

Tangent	Slopes
Auto	follow the neighbours and never overshoot them
Linear	point at the neighbouring keys
Free	set by hand; In and Out may differ

Before and After decide what happens outside the keys: Clamp holds the end value, Loop repeats, Ping-pong repeats mirrored. Curves are float32 and evaluate identically on every platform.

---

id: curves/editor icon: edit.rename parent: curves order: 2 title: Editing curves

Editing curves

The Inspector draws the curve inside the field; a click opens the curve editor.

• Preset switches between presets and Keys. Choosing Keys on a preset turns it into editable keys of the same shape.
• Double-click the graph to add a key on the curve, right-click a key to remove it, drag a key or a slope handle to change it.
• Hold Ctrl (Cmd on macOS) to snap to a 1/20 grid of the view, hold Shift while dragging a slope handle to move one side only.
• Time, Value, Segment and Tangent edit the selected key; dragging a handle makes its tangent Free.

Every drag is one undo step. Prefab instances show an overridden curve like any other field.

---

id: curves/scripts icon: file.script parent: curves order: 3 title: Curves in scripts

Curves in scripts

A script reads a curve field of a component and evaluates it with aego/curve:

import "aego/curve"

func Update(dt float) {
  age += dt
  fade := node.Get<Fader>().Alpha
  sr.Tint.A = curve.Eval(fade, age / curve.Duration(fade))
}

Function
Eval(c, t) float	the value at t, wrapped by Before and After
EvalClamped(c, t) float	the value at t clamped to the first and last key
Duration(c) float	time from the first to the last key, 1 for a preset
Ease(e, t) float	a preset easing at t clamped to 0..1

The constants curve.Linear, curve.OutQuad and the rest have the type curve.Easing and are the ease argument of tweens.

A Curve value is a read-only view of the field, not a copy: it sees edits made after it was read. Scripts cannot build curves or export curve fields. A view whose node or component is gone faults with AES6004.

---

id: curves/go icon: code.brackets parent: curves order: 4 title: Curves in Go

Curves in Go

type Fader struct {
  Alpha curve.Curve `aego:"alpha"`
}

c := curve.Keyed(curve.Key{T: 0, V: 1}, curve.Key{T: 0.5, V: 1, Interp: curve.InterpLinear}, curve.Key{T: 1, V: 0})
v := c.Eval(0.75)

Function
FromEasing(e), Line(t0, v0, t1, v1), Constant(v), Keyed(keys...)	construction
Eval, EvalClamped, Span, Duration, Range(samples)	reading
Fix, Smooth, Normalize, Bake(samples)	editing helpers

Keyed and Fix sort the keys, drop keys with NaN and keep the last of two keys at the same time. Change Keys directly only together with Fix or Smooth.

In scenes and prefabs a curve is written as a struct; defaults are omitted and a preset has no keys:

falloff={ ease=outQuad post=pingPong }
alpha={ keys=[[0, 1, 0, 0, bezier, auto], [1, 0, -2, -2, linear, free]] }