Figure 3.

Potential types of deformations in the CE model. (a) Original cell shape. (b) Deformation type A (perimeter preserved): initial side lengths are conserved while the Euclidean distance of pairs $(i,i+1)$ decreases. (c) Deformation type B (area conserved): side lengths are increased while the Euclidean distance of pairs $(i,i+1)$ is conserved. (d) One of the possible cases in deformation type C (vertex removed: the junction angle between a line $(v_i,v_{i+1})$ and $(v_{i+1},v_{i+2})$ becomes zero while the sum of initial side length of pairs $(i,i+1)$ and $(i+1,i+2)$ is conserved (a point $v_{i+1}$ is hidden inside of the straight line)).