LiquidMorphPhysics class

Pure, stateless math engine for liquid glass morphing animations.

This class implements the J-curve back-out position curve and Curves.linearToEaseOut / smootherstep size curve that together create the iOS 26 liquid teardrop morphing effect.

It is intentionally stateless — feed it the raw animation value plus the source/destination geometry and it returns a fully computed LiquidMorphState for that frame. No BuildContext, no State, no ChangeNotifier dependencies.

Design

Two conceptual blobs drive the morph:

• Blob A (anchor / ghost trigger) stays at the trigger position and shrinks away over the first 40 % of the animation to cleanly break the liquid bridge.
• Blob B (menu body) travels from the trigger center to the menu center along a J-curve overshoot trajectory, expanding from trigger size to menu size.

The metaball SDF shader automatically creates the teardrop neck between the two blobs — there is no explicit neck geometry.

Auto-Scaling

When compute receives a scaleDelta greater than 1.5, the engine engages adaptive mode:

• The J-curve back-out amplitude is reduced inversely with vertical travel so the physical overshoot stays within ~10–14 px regardless of the destination size. This eliminates the 35–40 px "plunge" seen when a large menu or full-sheet morph uses the small-menu constant.
• The size curve switches from Curves.linearToEaseOut to a smootherstep sigmoid (for scaleDelta > 3.0) that keeps the droplet compact through the detach/travel phases and blossoms rapidly only as it lands.
• Blend attenuation prevents excessive SDF merging at extreme scale ratios.
• Push momentum is bounded to a physical maximum so the trigger bounces with native-grade subtlety rather than a jarring multi-pixel jolt.

Usage

// Typically called from an AnimatedBuilder or addListener callback.
final state = LiquidMorphPhysics.compute(
  rawValue: controller.value,
  finalDx: finalDx,
  finalDy: finalDy,
  horizontalOffset: _horizontalOffset,
  verticalOffset: _verticalOffset,
);

// Apply to the UI:
Positioned(
  left: triggerX + state.pushDx,
  top:  triggerY + state.pushDy,
  child: Transform.scale(scale: state.anchorScale, child: blobA),
)

Properties

hashCode → int

The hash code for this object.

no setter, inherited

runtimeType → Type

A representation of the runtime type of the object.

no setter, inherited

Methods

noSuchMethod(Invocation invocation) → dynamic

Invoked when a nonexistent method or property is accessed.

inherited

toString() → String

A string representation of this object.

inherited

Operators

operator ==(Object other) → bool

The equality operator.

inherited

Static Methods

compute({required double rawValue, required double finalDx, required double finalDy, double horizontalOffset = 0.0, double verticalOffset = 0.0, double scaleDelta = 1.0, bool? adaptiveDamping, bool isClosing = false}) → LiquidMorphState

Computes the full LiquidMorphState for a single animation frame.

computeAdaptiveBackOutAmplitude({required double finalDy, double baseAmplitude = _backOutAmplitude}) → double

Computes the adaptive J-curve back-out amplitude for a given vertical travel distance.

computeBlendAttenuation(double scaleDelta) → double

Computes the SDF blend attenuation factor for a given scale ratio.

computeScaleDelta({required Size sourceSize, required Size targetSize}) → double

Computes the geometric scale ratio from sourceSize to targetSize.

Constants

closeSpring → const SpringDescription

Spring profile for the iOS 26 liquid morph closing animation.

closeVelocityHint → const double

Initial velocity hint injected when the close animation starts.

openSpring → const SpringDescription

Spring profile for the iOS 26 liquid morph opening animation.