Shader React Native Effects

ShaderView Effects

ShaderView renders a WGSL fragment shader on a WebGPU canvas with the render loop running off the JS thread (react-native-worklets). You write only the fragment shader; the library provides the full-screen triangle vertex shader and a fixed uniform buffer.

Quick start

import { useMemo } from 'react';
import { ShaderView, type ColorInput } from 'react-native-effects';

export default function MyEffect({ color = '#3b82f6' as ColorInput, ...viewProps }) {
  const colors = useMemo(() => [color], [color]);
  return <ShaderView fragmentShader={SHADER} colors={colors} {...viewProps} />;
}

const SHADER = /* wgsl */ `
struct Uniforms {
  resolution: vec4<f32>,  // (width, height, aspect, pixelRatio)
  time:       vec4<f32>,  // (seconds, dt, 0, 0)
  color0:     vec4<f32>,  // colors[0] RGBA 0..1
};
@group(0) @binding(0) var<uniform> u: Uniforms;

@fragment
fn main(@location(0) ndc: vec2<f32>) -> @location(0) vec4<f32> {
  let uv = ndc * 0.5 + 0.5;                              // y-UP: uv.y=1 is TOP
  let c = (uv - 0.5) * vec2<f32>(u.resolution.z, 1.0);   // aspect-corrected, centered
  let glow = 0.05 / (length(c) + 0.05);
  return vec4<f32>(u.color0.rgb * glow, 1.0);
}`;

Full uniform layout, props, live-input API, and WGSL gotchas: WGSL.md

Non-negotiable rules

1. WGSL, not GLSL. No ternary (select()), no frac (fract), explicit f32 literals (1.0 not 1), var mutable / let immutable.
2. Never name a variable active, auto, filter, final, new, target, mod, type, set, get, self, smooth, precise, common. These are WGSL reserved words; the shader compiles to a silent failure → blank canvas. This is the #1 cause of "nothing renders".
3. UV is y-up: uv.y = 1.0 is the TOP of the view. Negate when porting Shadertoy/screen-space logic.
4. transparent ⇒ premultiplied alpha: return vec4<f32>(col * alpha, alpha); — straight alpha washes grey where alpha→0.
5. Per-frame input goes through paramsSynchronizable (u.live), never React props/state — prop updates re-render and drop frames.
6. Shader string = module-level const; useMemo the colors/params arrays; spread ...viewProps.

Workflow for a new effect

1. Design before coding: pick 2–3 visual layers (base field → mid-scale structure → micro detail/highlight). Single-layer shaders look fake. Recipes: TECHNIQUES.md
2. Set a performance budget first: fragment cost × every pixel × DPR. Pick noise octaves and loop counts from PERFORMANCE.md, don't tune down later.
3. Write the component wrapper (Quick start above). Map design knobs to params (max 8 floats) and colors (max 2); live input via useParamsSynchronizable.
4. Build the shader incrementally — start by returning a solid color, then add one layer at a time so a silent compile failure is bisectable.
5. Verify on device with the argent tools (launch the example app, screenshot, compare against intent), then check motion smoothness at the final size.

Debugging a blank/black view

A blank view almost always means the WGSL failed to compile (silently). In order:

1. Grep your identifiers against the reserved-word list in WGSL.md.
2. Check for GLSL-isms: ternaries, vec3(x) shorthand without <f32>, int/float mixing, swizzle assignment (p.xy = ... is illegal).
3. Bisect: return vec4<f32>(1.0, 0.0, 1.0, 1.0); at the top of main, move it down until it breaks.
4. Verify the Uniforms struct fields are declared in the exact canonical order (top-down, may stop early).

Reference files

• WGSL.md — exact ShaderView contract: props, uniform slots, entry point, live input, reserved words, GLSL→WGSL translation
• TECHNIQUES.md — realism recipes: noise/fbm toolkit, cosine palettes, specular glare, glass, sparkle, domain warping, dithering, transparent overlays
• PERFORMANCE.md — cost model, octave/loop budgets, what's expensive on mobile GPUs, measuring on device
• In-repo exemplars: example/src/components/HoloFoilCard.tsx (tilt-driven foil), src/components/Aurora.tsx (fbm curtains), example/src/components/VoiceWave.tsx (audio + transparency), src/components/Campfire.tsx (3D simplex noise)

Source: blazejkustra/react-native-effects — distributed by TomeVault.