Cross lines in contour

I draw a TGraph2D object with option: contz plus cont3same (the plot is posted below). However, the contours look very weird, for example, some lines cross the whole region. Anyone could explain why? and how to avoid such an issue.


Do you have a macro reproducing this problem ?

Yes, the macro and its input histogram are attached.

derived_length.root (41.9 KB)
plot_topo_contour.C (2.86 KB)

I modified your macro.

plot_topo_contour.C (2.19 KB)