Abstract: An elastic body is modelled as a plurality of models of particles and models of geometric elements. Each particle model has a position attribute. Each geometric element has a boundary defined by two or more of the particles as nodes of the geometric element, nodes being points shared with neighbouring geometric elements. The interior area or volume of the geometric elements is modelled via non-linear interpolation functions that use the positions of the particles of the respective geometric elements as inputs to compute position and/or strain of interior points of the geometric elements. Energy is summed over the interior region of the element, the energy computation based on (a) position and/or stress of the geometric element computed by the non-linear interpolation functions and/or (b) non-linear material parameters that depend on position and/or strain at the interior points of the geometric elements. New positions of the particles are computed based minimizing total energy of the element.