The hit test result can give you the indices of the points of the selected triangle.

NHitTestResult result = nChartControl1.HitTest(e.X, e.Y);
NSurfaceTriangle tr = result.Object as NSurfaceTriangle;

You can pick the closest point from one of the three points that are indicated by tr.DataPointIndex1, tr.DataPointIndex2 and tr.DataPointIndex3. If you prefer you can use the points to calculate the exact coordinates of the 3D point under the mouse. We can also send you an example project that demonstrates this - please write to our support email if you need it.

Best Regards,
Nevron Support Team

I'm able to show tooltips with value (using new NInteractivityStyle("")), but this does not work for NTriangulatedSurfaceBase. Retrieving the X and Z is easy using NChartControl.HitTest(x, y), but this doesn't really help me in this case. The only workaround I've found is to manually search through all data points to figure out what point is closest to a given position and retrieve this value. Is there really not any better way to do this?