4d scatter plot

Hallo,
I would like to do a 4d scatter plot like the one in the link below:

root.cern.ch/drupal/category/ima … ics?page=1

(3rd row from the bottom)

but i have found no documentation/examples and for me it is not apparent how to do it.
do i use a TGraph2D? and how do i put the 4th dimension?

thanks,
theodoros

it is done with TTree::Draw when 4 variables are used.
ex:

root [1] ntuple->Draw(“px:py:pz:px*py”)