The recursive transfer method (RTM) provides a unique numerical means of extracting a localised wave in a scattering problem. However, various shapes of scatterers were hitherto difficult to adapt RTM, because mesh elements were limited to rectangles. In this study, we propose what we call mechanics shape function using subdivision triangles of a quadrilateral element, and we extend RTM to be valid for various shapes of scatterers. The effect of the mechanics shape function is evaluated using a uniform waveguide with a distorted mesh.