Prusa ColorMix Shading: Fake Studio Lighting Baked Into Your Filament

Miniature painters have sprayed zenithal highlights for decades — dark primer on the base, white from above, and gravity does the work. Prusa’s ColorMix Shading app does the same thing digitally, before the print even starts, using filament mixing ratios instead of spray cans.

Why This Category / Comparison Matters

Multi-color printing has focused almost entirely on color placement — putting red here and blue there. What it hasn’t done well is depth and dimensionality. Flat multicolor prints still look flat. Zenithal shading — placing lighter colors on top-facing surfaces and darker colors on bottom-facing ones — is how both painters and photographers create the illusion of three dimensions. Bringing that into a slicer workflow closes a gap that’s existed since multi-filament printers shipped.

What Makes It Different

The ColorMix Shading app is a free, open-source web tool (MIT license) that works entirely in-browser. Upload an STL, OBJ, or 3MF file, pick your highlight and shadow colors, set the number of mix steps (1–3 recommended for distinct gradations), and position the virtual light using an interactive gizmo. The app calculates per-face color ratios based on surface angles relative to the light source, then exports a 3MF file ready for PrusaSlicer or EasyPrint.

Compatible printers span Prusa’s multicolor lineup: XL (the recommended option for best results), MK4S with MMU3, CORE One+, and the upcoming INDX upgrade for CORE One+. Even single-material printers can achieve a version of the effect with careful dark/light filament selection, though without dynamic mixing.

The visual results are immediate on organic models — sculptural busts, terrain maps, and figurines all benefit dramatically from the depth that zenithal shading provides. Because the shading is encoded as actual filament ratios rather than a paint layer, it’s fully durable and requires no post-processing.

The Catch / Who It’s For

The technique requires a multi-material printer to get smooth gradient transitions. Single-filament printers can approximate the effect with only two tones (highlight and shadow), but gradual transitions need three or more mix steps across compatible hardware. The app also doesn’t handle undercuts or complex shadow geometries — it models a single overhead virtual light, not physically accurate ray tracing.

Hermes Desktop is for Prusa multi-material printer owners looking to add dimensionality to figurines, terrain, busts, and decorative models. It’s less relevant for functional printing where color aesthetic doesn’t matter.

Source: Prusa Blog

Content created with AI assistance and reviewed for accuracy.