Addon for Blender 3.x – smoothing mesh surfaces without volume loss. Since ver 2.3 update there is also ‘Volume smooth brush’ tool (has geometry sliding option) available in edit mode.

Latest version of VPSmoothing – 2.6.0 – supports only Blender 3.6 (as of today 29.07.2023) .

For previous versions of Blender (below 3.6) use VPSmoothing 2.54

Video guide – bit old – there was no smooth brush yet.

Volume Preserving Smoothing takes also into account sharp edges – they will be treated as rails for verts to slide on. This can help to maintain main shapes of smoothed object.

To access the smoothing operator (works on whole mesh or selection): open mesh context menu with W key in mesh edit mode, then select Mesh Smoothing visible at the very bottom, and pick mode:

Inflate smoothing – good for round surfaces

Laplacian HC smoothing – fast but sometimes give artifacts

Volume smoothing – slower but best quality

To use smooth brush: open left tools sidebar (T – key in 3d view), enable ‘Volume smooth tool’ icon.

Features:

smooth mesh while maintaining main object shape (operator and brush)

border mesh vertices will slide along border edges, this prevents shrinking of mesh outline

smooth brush support pulling/sliding of geometry along surface of mesh

X axis symmetry is supported

works with shape-keys

you have ability to define sliding rail edges (edges marked as sharp) – they constrain sliding of geometry

three edge tension methods (Uniform, Proportional to edge length, Inverse to edge length)

optimized with NUMPY

To make edge into rail edge – just mark edge loop as sharp. Now verts belonging to this edge, will move only along edge.
Last update 2.6.0 (28.07.2023) – For Blender 3.6 and up

added ability to work on very small objects (minimum brush size is now linked to 0.001 of object size),

Moved from old bgl module to gpu module (from now on only blender 3.6 and up will be supported)

Last update 2.8.0 ( 26.11.2023 – For Blender 3.6, 4.x)

Smooth Operators now support masking the effect by Vertex Group (see F9 Vertex Mask property)

Adjusting Smooth brush size with F and strength with Shift+F wont move brush outline anymore (more in line with Blender brush behavior),

Fix brush strength number not being visible in UI when adjusting it,

Last update 2.9.0 ( 16.10.2024 – For Blender 3.6, 4.x)

Pull strength can be adjusted with Ctrl+Shift+F key,