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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⁡((t−1)⋅π2)+1f(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)
}