Sculpt: Sharpen Mesh Filter

This mesh filter sharpens and smooths the mesh based on its curvature,
resulting in pinching hard edges and polishing flat surfaces. It fixes
most of the artifacts of the voxel remesher and those produced when
sculpting hard surfaces and stylized models with creasing and flattening
brushes.

It needs and accumulate_displacement step before each filter iteration which
can't be multithreaded in an easy way (it would need something to sync the
threads when modifying the data of neighbors in a different node), but this
does not affect performance in a significant way.

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D7335

release/scripts/startup/bl_ui/space_toolsystem_toolbar.py

@@ -1034,6 +1034,8 @@ class _defs_sculpt:
             if (props.type == "SURFACE_SMOOTH"):
                 layout.prop(props, "surface_smooth_shape_preservation", expand=False)
                 layout.prop(props, "surface_smooth_current_vertex", expand=False)
+            if (props.type == "SHARPEN"):
+                layout.prop(props, "sharpen_smooth_ratio", expand=False)
 
         return dict(
             idname="builtin.mesh_filter",