Hello everyone,thanks to your help,I can make my 2D tree-structured work now.
Now I'd like to push it forward into 3D space,however,my code doesn't work in the way it should.I see nothing apart from black all the way.My attempt to debug failed again and again,could you help me to figure out what happened?Thank you.

Here is my attempt:When one cube is left clicked its children appear and when right clicked its children disappear along with itself.The key is to add a cut in,display and fade out effect for each node.
For the purpose of simplicity,I designed "control rectangle" to respond to a click instead of an algorithm to judge the cursor's position.

Please access my code at
http://www.rayfile.com/files/7a298e70-1ce3-11de-bd97-0014221b798a/
Iif you are kind enough ,please copy and paste  it  directly to your processing interface and have a look.Thank you!