3D Lasso on a volume

I’m looking for an algorithm or an example for a 3D Lasso on 3D Volume.
I was looking for VtkVolumePicker class, but in the example there is no volume that is input into that class, all I see is picker.Pick(x,y,0,ren).
Can you point to me an algorithm to achieve 3D Lasso rendering on a selected volume using mouse?

Any suggestions for the steps required ?

This feature is not implemented in VTK but you can easily add it to your VTK-based application. See more information on the implementation in 3D Slicer here.

Thanks for your quick reply and your help.

Can you show me the place where I draw the lasso curve by mouse points ?