Fillets and chamfers where edges meet at corners on a curved wall or a knife-edge tip (#851) (#935)

Rolling-ball blends now handle knife edges, where the two faces have opposite normals; an edge that runs out along an end face tangent to one side; and rounds that end in an earlier round on curved faces, picked together or one after another. The three edges at a vertex of smooth faces, rounded to one radius, end in a piece of sphere. When the given order of up to four edges is refused, or leaves a face boundary off its surface, other orders are tried.

Closes #851.

Co-authored-by: lasselian <22126420+lasselian@users.noreply.github.com>

crates/kernel/src/lib.rs

@@ -15,6 +15,7 @@
 mod blend;
 mod blend_corner;
 mod blend_variable;
+mod blend_vertex;
 mod body;
 mod boolean_diagnostics;
 mod boolean_guard;
@@ -44,6 +45,8 @@ mod issue_616_tests;
 mod issue_674_tests;
 #[cfg(test)]
 mod issue_679_tests;
+#[cfg(test)]
+mod issue_851_tests;
 mod lip;
 mod loopblend;
 mod measure;