Figure 9 in Morphometrics: History, development methods and prospects

Figure 9. Left. Representation of the surface of the Kendall shape space for triangles with the pole position occupied by an equilateral triangle. Each point on the surface of the sphere represents a unique configuration of 3 2D coordinate points as illustrated by the triangle diagrams. Note isosceles triangles occupy a meridian, right triangles that verge left or right occupy two meridians, and colinear triangles occupy the equator. Triangles in the lower hemisphere of this shape space are reflections across the baseline of triangles in the upper hemisphere. These two hemispheres collapse under Procrustes alignment as the lower hemisphere triangles are rotated to match the shapes of the upper hemisphere triangles. Right. Principal components ordination of 500 Procrustes-aligned random triangle configurations.