Prusa ColorMix in PrusaSlicer 2.9.6 Beta: Paint the Model, Skip the Setup

Despite being the one manufacturer that has offered a mature, purge-free multimaterial 3D printer for years (the Prusa XL – released 2023) Prusa Research has taken its cautious time to implement 3D printing’s hottest new color mixing trend. To recap quickly, if you stack thin layers of different colors together in a print, they look like a different color altogether.

It’s an optical illusion, but one that slicers are now rapidly being adapted to control, letting you deliberately create many more virtual filament colors from the base materials loaded in your system.

Prusa’s approach is a straightforward evolution that uses the convenience of its EasyPrint cloud slicer to frame the idea that the virtual colors should simply be there for you to use, rather than be something you have to consciously figure out first.

The Prusa ColorMix model, published under MIT licence as prusa3d/prusa-fdm-mixer on GitHub, is built on the Yule-Nielsen halftone equation the company explains in a blog post. It’s the same bit of math used to model how dots of color ink on paper can produce a consistent tone, but with empirical corrections fitted against readings of actual printed Prusament PLA on a Prusa XL.

This sets Prusa’s work apart from the original OrcaSlicer-FullSpectrum and implementations like Bambu Studio’s Color Mixer Studio, which both use Justin H. Rahb’s filament-mixer library. While that works in a slicer to better visualize the result of mixing two specified filament colors, it doesn’t always reflect the printed reality. Instead, Prusa has rebuilt the prediction aspect against measurements taken from actual printed results.