Figure 2.

Pseudopod and tangent to surface. The pseudopod algorithm identifies growing pseudopodia by three steps: (i) it identifies a series of adjacent convex nodes, (ii) evaluates the ‘bending’ of the convex nodes, and (iii) sets a minimal growth area. Then the algorithm searches the central convex node (yellow) in the two frames where the area change became positive for the first time (start) and was positive for the last time (end), respectively. The arrow connects these points, and represents the growing pseudopod as a vector with length, timing and directionality. The slope of the tangent to the surface at a specific node (yellow node) was calculated as the weighted average of the angles between a node and its adjacent node up to three nodes away from the central convex node.