Fig. 4

Linear approximation of the geometry (zero level set contour) given a surface triangulation for the femur bone. The grey balls indicate the nodes of the original surface triangulation. All elements with positive level set values in all their nodes are shown in red, all elements with a change in sign of the level set value (containing the zero contour line of the level set function) are shown in green and all elements with negative level set values in all their nodes are shown in blue