Smoothen of flatten selected shading normals

This tool can be applied to polygonal SDS objects, which have the Phong shading option set. To use it, set the target object to the edit mode, select some faces/edges/points and apply the tool. Clicking the tool icon toggles between smooth and sharp shading normals. From the side menu, the desired alternative can be chosen directly as follows:

Smoothen selected shading normals

Sets the phong shading normal of every face passing trough a selected point to the common average normal. Phong shading interpolates smoothly over the selected points.

Flatten selected vertex normals

Sets the phong shading normal of every face passing trough a selected point to the geometric normal of the polygon corner in question (computed from the two surrounding polygon edges). Phong shading does not interpolate the normal smoothly but uses a private normal per face per selected point.