Although I am unaware how to do this, or it’s kind of a feature request 
When one draws TGraph2D in “tri*” mode and than attempt to zoom an axis, triangles are recomputed. So if a point of a triangle close to edge is no longer visible on the graph, the triangle also becomes missing and we’ve got a hole in the graph. When zooming I’d like to simply get zoomed to a part of a graph I am already seeing on the screen - thus in the TGraph2D case, close to the edge I would have just parts of triangles, that are continued outside of the zoomed area. Is it possible?
Yes, only the visible triangles are shown. There is no 3D clipping.