Spring animation

Physics-based spring animations, decay/inertia, and rubberband boundary constraints for Unity.

com.bluecadet.spring drives values toward targets with a damped harmonic oscillator (SpringValue<T>), decays velocity to rest for momentum-based motion (DecayValue<T>), and applies iOS-style elastic resistance at boundaries (Rubberband). Per-type math is Burst-compiled for float, Vector2, and Vector3.

Requirements

• Unity 6000.3+
• com.unity.burst 1.8.27
• com.unity.mathematics 1.3.3

Install

OpenUPM is the recommended path:

openupm add com.bluecadet.spring

The scoped registry (https://package.openupm.com, scope com.bluecadet) only needs adding once per project.

To install from a Git URL instead, point at the release tag, which follows the com.bluecadet.spring@<version> format:

{
  "dependencies": {
    "com.bluecadet.spring": "https://github.com/bluecadet/unity-packages.git?path=Packages/com.bluecadet.spring#com.bluecadet.spring@<version>"
  }
}

Pick a version from Releases — every released tag is listed there. The openupm add form above always takes the latest.

Quick start

A basic spring

using Bluecadet.Spring;

// Create once (e.g. in Awake), hold as a field
_spring = Spring.Create(0f)
    .WithDamping(26f)
    .WithStiffness(170f)
    .Bind(x => transform.localPosition = new Vector3(x, 0, 0));

// Animate to a target (velocity is preserved mid-flight)
_spring.To(1f);

// Release when done (e.g. OnDestroy)
Spring.Release(_spring);

A decay

_decay = Spring.CreateDecay(Vector2.zero)
    .WithFriction(8f)
    .Bind(v => scrollView.velocity = v);

// Trigger on swipe
_decay.Play(swipeVelocity);

Spring.Release(_decay);

A rubberband clamp

using Bluecadet.Spring;

// Resist a value past its bounds (e.g. during drag)
float constrained = Rubberband.Apply(value, min: 0f, max: 100f, resistance: 0.55f);

// Snap back to bounds on release
if (Rubberband.IsOutOfBounds(position, 0f, 100f))
    _spring.To(Rubberband.Clamp(position, 0f, 100f));

Next

• Springs and decay — builder options, binding, events, and lifetime for SpringValue<T> and DecayValue<T>.
• Rubberband — the static Rubberband API and a worked drag/release example.