Voxel based modeling is an attractive way to represent complex multi-material objects. Multi-labeled voxel models are also ubiqui- tous in material sciences, medical imaging or numerical simulations. We present here a variational method to regularize interfaces in multi-labeled digital images. It builds piecewise smooth quadran- gulated surfaces efficiently, with theoretical guarantees of stability. Complex topological events when several materials are considered are handled naturally . We show its usefulness for digital surface approximation, for voxel art regularization by transferring colori- metric information, and for upscaling voxel models to speed up coarse-to-fine modeling.