Mesh internal surface smoothing behavior changed in

It seems that the rewrite of vtkWindowedSincPolyDataFilter (that amazingly improved its performance) also changed how internal surfaces are smoothed. Smoothing of internal surfaces are important because when we segment a medical image we usually annotate many adjacent structures that have common surfaces and when we apply smoothing then we want to smooth surface of each structure and not just the outer surface of the entire segmented region. The old version (VTK8) smoothed the internal surfaces

Dynamic mesh approaches for eroded shape predictions - ScienceDirect

Understanding the effects of mesh smoothing methods in the CFD modelling of Zhundong lignite ash deposition - ScienceDirect

This internal standpipe design allows for a larger screen surface area

Mesh Smoothing - an overview

Predicting stress, strain and deformation fields in materials and structures with graph neural networks

A hexahedral-dominant FE meshing technique using trimmed hexahedral elements preserving sharp edges and corners

Smooth

a. Tri mesh before smoothing

Illustrative concepts of conforming mesh and non-conforming mesh.