Chroma-gated, differentiable OKLCH interpolation: Continuous Oklab fallback for color-cast reduction

This paper proposes Continuous Oklab fallback (COFb), a one-parameter chroma gate that blends OKLCH interpolation toward linear Oklab as chroma drops. The goal is to reduce the “color-cast” problem in gradients: not just the achromatic-endpoint bow that existing two-valued switches handle, but also the inter-hue detour where chromatic colors sweep through an unintended hue.

The practical appeal is that it stays differentiable and avoids endpoint tests. The author characterizes a trade-off frontier between cast reduction and hue preservation, then recommends a default of n=1 with σ≈0.19 for a typical sRGB palette. At that setting, the paper reports roughly a 49.5% reduction in mean lateral deviation and a 35.5% reduction in chroma-weighted hue excursion.

For game devs, this is mostly a rendering and tooling concern. If you’re building gradient editors, UI theming, post-processing, or shader-based color ramps, the method gives you a fallback path that behaves more like modern OKLCH interpolation while running entirely in plain Oklab (a,b) to sRGB. That makes it useful where CSS Color 4 features aren’t available, or where you need the same look in older engines and offline image/video pipelines.

The paper is also explicit about limits: on the classic “one endpoint is achromatic” case, the older two-valued switch still wins, and COFb does not preserve chroma because it is still a Cartesian blend under the hood. So this is not a universal replacement for OKLCH; it’s a pragmatic compromise for reducing the most visible hue casts in real production paths.