Pigment Layering: Kubelka–Munk Paint Mixing

This simulator lets you paint directly onto a 3D canvas and watch translucent pigment layers build up physically rather than as flat blended colors. Every brush stroke deposits a real pigment — Titanium White, Cadmium Yellow, Cadmium Red, Ultramarine, Phthalo Green or Burnt Umber, each with its own tinting strength — that mixes with what is already on the canvas using the Kubelka–Munk two-constant reflectance theory used to model how paint actually absorbs and scatters light. Layer enough passes and the canvas grows a visible impasto height, while a live toggle lets you compare the same brush stroke under physical subtractive mixing against a naive RGB blend, showing exactly why blue and yellow paint mix to green in real life but to grey under a simple average.