2. Face normals and vertex normals

Flat vs. smooth, and splitting by angle.

Shape

Segments

Normals Flat (face normals) Smooth (vertex normals)

Split by angle Angle threshold Light direction (left/right) Light height Toon shading Toon threshold Show vertex normals

Triangles: · Drag the view to turn it.

Flat: all three corners of a triangle use the face normal. The triangle has one brightness and looks faceted.
Smooth: each vertex gets the average of the surrounding face normals, and the triangle blends the three. It looks round, but the outline stays angular.
Try “Split by angle” on the cylinder. Side faces meet at 360° ÷ segments, the top meets the sides at 90°. A threshold between the two keeps only the sides smooth.
Turn on “Show vertex normals” to see places with several normals at one position (split vertices).