When blending a pair of edges of the same convexity, two blend surfaces are constructed – one per edge. The vertex is not blended in this case; rather, new edges are created at intersections of blend surfaces.

However, when blending a pair of edges of opposite convexity, the vertex where the edges meet is automatically blended.

Blending a pair of edges of the opposite convexity is impossible for chamfers.

Blending a pair of edges of the same convexity |
Blending a pair of edges of the opposite convexity |