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Reanimated + Skia Performance

Defaults

• Keep animation state on the UI thread: useSharedValue, useDerivedValue, worklets.
• Prefer Reanimated v4 declarative APIs; avoid legacy Animated.
• Prefer shared.get() / shared.set() over shared.value in app code (React Compiler friendly).
• Minimize JS↔UI crossings: avoid scheduleOnRN/runOnJS except for unavoidable side effects.
• For Skia, avoid per-frame React renders: pass SharedValues directly to Skia props/uniforms.

Workflow

1. Define the effect: what animates, duration/curve, interrupt rules, and gesture input.
2. Choose the renderer:
   • Use Reanimated styles for transforms/opacity/layout.
   • Use Skia for custom drawing, particles, gradients, runtime effects/shaders.
3. Choose the primitive:
   • Use Reanimated CSS transitions/animations for simple declarative style changes.
   • Use withTiming for tweens, withSpring for physics, withDecay for momentum.
   • Use Layout Animations for mount/unmount or layout changes.
4. Implement a single data flow on the UI thread (no setState per frame).
5. Do a perf pass (see references/perf-checklist.md).

Patterns

Shared values (React Compiler safe)

• Read: progress.get()

• Write: progress.set(withTiming(1))

  import { useEffect } from 'react'; import { useSharedValue, withTiming } from 'react-native-reanimated';

  const progress = useSharedValue(0);

  useEffect(() => { progress.set(withTiming(1, { duration: 400 })); }, [progress]);

Reanimated v4 CSS transitions

Use for state-driven style changes where you do not need bespoke worklets.

import Animated from 'react-native-reanimated';

<Animated.View
  style={{
    width: expanded ? 240 : 160,
    opacity: enabled ? 1 : 0.6,
    transitionProperty: ['width', 'opacity'],
    transitionDuration: 220,
    transitionTimingFunction: 'ease-in-out',
  }}
/>

Reanimated v4 CSS animations (keyframes)

Use for keyframe-like sequences (pulses, wiggles, repeated loops) without writing custom worklets.

Supported settings:

• animationName (keyframes object)

• animationDuration

• animationDelay

• animationTimingFunction

• animationDirection

• animationIterationCount

• animationFillMode

• animationPlayState

  import Animated from 'react-native-reanimated';

Dev-mode tuning panel (sliders)

Use sliders to tune animation configs or shader uniforms in __DEV__.

• Keep the tuning UI in a separate component to avoid re-rendering the animated scene.
• Write slider values into SharedValues via .set().
• For shader tuning: feed SharedValues into uniforms via useDerivedValue.
• For animation config tuning: store config params in SharedValues and read them when starting/restarting the animation.

See: references/dev-tuning.md.

Gesture-driven animation (Gesture Builder API)

Update shared values in onUpdate and drive visuals via animated styles.

import { Gesture, GestureDetector } from 'react-native-gesture-handler';
import Animated, { useAnimatedStyle, useSharedValue, withSpring } from 'react-native-reanimated';

const x = useSharedValue(0);
const gesture = Gesture.Pan()
  .onUpdate((e) => {
    x.set(e.translationX);
  })
  .onEnd(() => {
    x.set(withSpring(0));
  });

const style = useAnimatedStyle(() => ({ transform: [{ translateX: x.get() }] }));

<GestureDetector gesture={gesture}>
  <Animated.View style={style} />
</GestureDetector>;

Skia shader with animated uniforms

• Compile the runtime effect once (useMemo).

• Pass uniforms as a SharedValue<Uniforms> (Skia detects animated props by { value: T }).

• Do not access .value in your app code; pass the SharedValue object.

  import { useMemo } from 'react'; import { Skia, Canvas, Fill, Paint, Shader, type Uniforms } from '@shopify/react-native-skia'; import { useDerivedValue } from 'react-native-reanimated'; import { useClock } from '@shopify/react-native-skia';

  const sksl = ` uniform float2 u_resolution; uniform float u_time;

  half4 main(float2 xy) { float2 uv = xy / u_resolution; float v = 0.5 + 0.5 * sin(u_time * 0.002 + uv.x * 8.0); return half4(v, v * 0.6, 1.0 - v, 1.0); } `;

  const effect = useMemo(() => Skia.RuntimeEffect.Make(sksl), []); if (!effect) return null;

  const clock = useClock(); // ms since first frame const uniforms = useDerivedValue<Uniforms>(() => ({ u_resolution: Skia.Point(width, height), u_time: clock.get(), }));

  <Canvas style={{ width, height }}> <Fill> <Paint> <Shader source={effect} uniforms={uniforms} /> </Paint> </Fill> </Canvas>;

Common pitfalls

• Do not read shared values in React render; read them in worklets (useAnimatedStyle, useDerivedValue).
• Do not call runOnJS/scheduleOnRN in onUpdate unless you must.
• Do not allocate big arrays/paths/images per frame; memoize Skia objects and update via animated props.
• For runtime effects, always provide every uniform declared in the shader; missing uniforms throw.

References

• Reanimated v4 patterns and repo conventions: references/reanimated-v4.md
• Skia Canvas + runtime effects/shaders patterns: references/skia-shaders.md
• Dev-mode tuning panels (sliders): references/dev-tuning.md
• Performance checklist + debugging: references/perf-checklist.md

Weekly Installs

292

Repository

andreev-danila/skills

GitHub Stars

22

First Seen

Jan 20, 2026

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