How does on plot 3D countour

I would like to plot xyz points with intensity color

i know how to used TGraph2D

but I would like to plot x y z Counts which is read from ASCII file

into a 3D plot like TGraph2D with countour

Use the TGraph2D constructor which reads and ASCII file. See:

thanks for the note but

i think i was not clear on this. i have some intensity measurement of a cylindrical crystal in x,y,z coordinate and i would like to plot the intensity as (x,y,z,I)

You need a TH3 in that case.