sineIn: Sinusoidal Acceleration

Smooth trigonometric acceleration with natural curved onset

The sineIn function creates gentle acceleration through sinusoidal mapping. This produces smooth curved motion that feels natural and organic compared to polynomial alternatives.

$f(t) = \sin\left((t-1) \cdot \frac{\pi}{2}\right) + 1$

The sinusoidal relationship provides smoother acceleration than linear functions while remaining gentler than polynomial curves, creating naturally flowing motion characteristics.

Live Editor

const fragment = () => {
  const w = 0.01
  const t = iTime.fract()
  const y = sineIn(t)
  const Y = sineIn(uv.x)
  const a = vec3(0.6, 0.9, 0.3)
  const b = vec3(0.9, 0.3, 0.7)
  const c = a.mix(b, y).mul(uv.x.step(t))
  const lines = mmin2(smoothstep(0, w, uv.mod(0.1).min(uv.sub(vec2(t, y)).abs())))
  const curve = stroke(uv.y.sub(Y), 0, w).mul(c)
  const color = lines.oneMinus().mul(0.2).add(curve)
  return vec4(color, 1)
}

Result

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