my own geometry has no lighting

I draw the pipe with several triangle(with some reasons, i can not use PolylineVolumnGeometry, bacause more than two lines may connect at one point),but i found that it do not hava linghting,the picture is:


The geometry most likely does not have normals or has the wrong normals. Check out this draft tutorial:

It is out of date, but the section on normals should give you the theory you need.