Getting interpolation info in TGraph2D


I have been using TGraph2Ds to create plots in COLZ style where the significance is plotted on the z-axis.
Now I want to draw a line to separate between which points (x,y) are above a specific significance value (1.6) and which below.

What I thought was to get all the interpolated values of the z-axis and whenever that value is 1.6, to plot that point. Then I could connect these points with a line.

So, after inserting all the points I wanted with graph->SetPoint(npt,xval,yval,zval); I tried using the Interpolate function for random x and y, but it breaks.

Any ideas on how to proceed on this? Is my idea feasible?



Your idea seems feasible, but it is not clear the problem you are having. Maybe if you post a small example with the problem it is easier for us to help you

Best Regards