- along extent (towrds +ve v) unit vector
- along traverse (towards +ve w) unit vector
'''
- p, normal, vec_v, vec_w = m.h.dtails(**m._vw2tiu_kw(v,w))
+ p, normal, vec_v, vec_w = m.h.details(**m._vw2tiu_kw(v,w))
if w > m.nt:
normal = -normal
vec_w = -vec_w