Hi feirui445, there are some previous examples here about how to approach things by making extended shapes that are booleaned rather than building things in a "fill in a 3D wireframe patch by patch" type manner, they might be applicable:

http://moi3d.com/forum/index.php?webtag=MOI&msg=10210.16
http://moi3d.com/forum/index.php?webtag=MOI&msg=4865.2

- Michael