Flow

The item URL works with no components.json setup. Files land in your tree and npm dependencies install alongside; the shader needs vgpu's WGSL loader wired once, in Setup.

The full entry shader, flow.wgsl. Copy it and it is yours.

// effect 010 · flow — pointer-stirred liquid, one pass, no simulation.
// Layered domain-warped fBM: a base field warps a second, finer one, and the
// pointer displaces the warp domain with a velocity bump that falls off
// smoothly around the cursor, so stirring visibly drags the flow.
// Works in linear light; encodes to sRGB once at the end.

import { fbmSimplex2d } from "@vgpu/wgsl-std/noise/simplex";
import { mixOklab } from "@vshaders/color/oklab";
import { linearToSrgb3 } from "@vgpu/wgsl-std/color";

// Tunable members follow resolution/time. Defaults live in lib/effects.ts and
// must be set by the runner: an unset uniform member reads as zero. Members are
// ordered so each vec3f lands on a 16-byte boundary with an f32 in its pad.
struct Uniforms {
  resolution: vec2f,
  time: f32,
  // Noise frequency: how many field features fit across the card.
  scale: f32,
  // Gradient endpoints, linear light (defaults: #0070f3 blue, #00DFD8 cyan).
  colorA: vec3f,
  // Multiplies time in every animation term.
  speed: f32,
  colorB: vec3f,
  // Radius of the stir bump around the pointer, in centered field units.
  stirRadius: f32,
  // Pointer position, physical pixels; canvas center before any interaction.
  pointer: vec2f,
  // Smoothed pointer velocity, physical pixels per second; zero when idle.
  pointerVelocity: vec2f,
  // How far one field-unit-per-second of pointer speed displaces the domain.
  stirStrength: f32,
  // Ground the effect sinks into at the edges, linear light: expose it so
  // the effect sits on any page, not just this gallery's ink.
  backgroundColor: vec3f,
}

@group(0) @binding(0) var<uniform> uniforms: Uniforms;

@fragment
fn main(@builtin(position) position: vec4f) -> @location(0) vec4f {
  let res = max(uniforms.resolution, vec2f(1.0));
  let uv = position.xy / res;
  let aspect = res.x / res.y;
  let p = (uv - vec2f(0.5)) * vec2f(aspect, 1.0);
  // The pointer transforms exactly like position; velocity scales by the same
  // pixels-to-field factor (1 / res.y on both axes after the aspect stretch).
  let pointerField = (uniforms.pointer / res - vec2f(0.5)) * vec2f(aspect, 1.0);
  let velocityField = uniforms.pointerVelocity / res.y;
  let t = uniforms.time * 0.08 * uniforms.speed;

  // The stir: displacement proportional to pointer velocity, under a Gaussian
  // falloff so it dies out smoothly past stirRadius.
  let offset = p - pointerField;
  let radius = max(uniforms.stirRadius, 1e-3);
  let falloff = exp(-dot(offset, offset) / (radius * radius));
  let stir = velocityField * uniforms.stirStrength * falloff;

  // Layered warp: the stirred base field steers a finer second octave layer.
  let q = (p - stir) * uniforms.scale;
  let base = fbmSimplex2d(q + vec2f(0.0, t * 1.4), 4, 2.0, 0.5);
  let fine = fbmSimplex2d(q * 1.9 + vec2f(base * 1.2 - t, base * 0.8 + t * 0.7), 4, 2.0, 0.5);
  let band = base * 0.55 + fine * 0.45;

  // Perceptual gradient through the band; a sheen where the layers agree
  // gives the surface its gloss.
  let blend = smoothstep(-0.55, 0.95, band);
  var color = mixOklab(uniforms.colorA, uniforms.colorB, blend);
  let sheen = smoothstep(0.35, 0.85, fine) * smoothstep(0.1, 0.7, base);
  color = mixOklab(color, vec3f(0.75, 0.95, 1.0), sheen * 0.3);

  // Churned regions glow toward white-cyan, so the wake of a stir reads even
  // after the displacement itself is subtle.
  let churn = min(length(stir) * 2.0, 0.6);
  color = mixOklab(color, vec3f(0.85, 0.97, 1.0), churn * 0.5);

  // Sink the edges into the page ink.
  let vignette = smoothstep(1.2, 0.4, length(p));
  color = mixOklab(uniforms.backgroundColor, color, 0.15 + 0.85 * vignette);
  return vec4f(linearToSrgb3(clamp(color, vec3f(0.0), vec3f(1.0))), 1.0);
}