PK_ERROR_code_t     PK_EDGE_is_smooth
(
--- received arguments ---
PK_EDGE_t           edge,       --- edge to test
double              max_angle,  --- maximum angle between face normals

--- returned arguments ---
PK_LOGICAL_t *const is_smooth   --- whether the edge is smooth
)


 This function checks whether the edge passed to it in edge is smooth
according to the angular criterion passed in max_angle.


 The condition for smoothness is defined as being that the angle between the
normals of the two faces that meet at the edge does not exceed the angle
supplied by the application along the edge.
 Note that edges to which this definition of smoothness is not applicable, such
as laminar edges, will always test false.