Fig. 2.

Atlas construction: template shape (left) and parameterization of the template-to-subject deformations (right). The template is initialized with an ellipsoid per connected components (top-left). After the optimization, the template shapes still have the same topology as the sample shapes. Simultaneously, template-to-subjects deformations are estimated, which are parameterized by the momentum vectors (red arrows). The vectors are located at the position of the control points, which are the same for all subjects. Control point positions were initialized as the nodes of a regular lattice, and our algorithm moves the control points to their optimal position near the surfaces and selects the most relevant ones according to the sparsity prior.