Vertex normal

 ( Shading ) 

In the geometry of computer graphics, a vertex normal at a vertex of a polyhedron is a directional vector associated with a vertex, intended as a replacement to the true geometric normal of the surface. Commonly, it is computed as the unit vector average of the of the faces that contain that vertex.Henri Gouraud. "Continuous Shading of Curved Surfaces." IEEE Transactions on Computers, C-20(6) : 623--629 (June 1971).Andrew Glassner, I.6 Building vertex normals from a unstructured polygon list, in Graphics Gems IV, edited by Paul S. Heckbert, Morgan Kaufmann, 1994. pp. 60--74 The weighted average for example by the area of the face or it can be unweighted.Nelson Max, Weights for Computing Vertex Normals from Facet Normals, Journal of Graphics Tools, Volume 4, Issue 2, 1999 p. 1-6Grit Thürrner and Charles A. Wüthrich, Computing Vertex Normals from Polygonal Facets. Journal of Graphics Tools, Volume 3, Issue 1, 1998. pp. 43-46 Vertex normals can also be computed for polygonal approximations to surfaces such as NURBS, or specified explicitly for artistic purposes. Vertex normals are used in Gouraud shading, Phong shading and other . Using vertex normals, much smoother shading than /ref>

• Specular highlight
• Per-pixel lighting