move_origin(rr,y,y0,ODefn,OOrgn,NDefn,NOrgn) :- !, 
	sel(ODefn,y=y0,y=0,NDefn1),		% special axis and
	subst(x=x+y0/tan(Trr),NDefn1,NDefn2),
% simplify NDefn2
	ncc tangent(axis(rr),[Trr,0]),		% fibre coordinate
	ncc tangent(axis(y),[Ty,0]),		% are at angle
	gensym(origin,NOrgn),
	fn_dbentry( on(NOrgn,axis(r)) ),
	fn_dbentry( separation(OOrgn,NOrgn,y0/cos(Ty-Trr),[Trr,0]) ).




