Fig 1. Two-dimensional cell model.

a) An isolated cell is modeled as a disk. b) A cell is modeled as a disk segment when contacting other cell(s). An outer edge e _i is an arc or a circle, representing the boundary between cell c _i and the outside medium (denoted as c ₀). An inner edge e _i,j occurs when a cell c _i is in contact with another cell c _j. Their shared boundary is modeled as a straight line segment. When two cells c _i and c _j make contact, their outer edges (arcs) e _i and e _j intersect at two vertices v _i,0,j and v _j,0,i, which are also the two end-points of the inner edge e _i,j. c) When three cells c _i,c _j and c _k intersect, they form a vertex v _i,j,k. d) A cell completely surrounded by other cells is represented as a polygon.