Hi Joel,
You can think of the triangulated surface data as if it is a table with 3 columns (x, y, z). The columns themselves do not differ from the other double series and therefore can be indexed - for example:
// add the point [10, 10, 10]
surface.XValues.Add(10);
surface.YValues.Add(10);
surface.ZValues.Add(10);
// then modify that point to [20, 20, 20]
int lastIndex = surface.XValues.Count - 1;
surface.XValues[lastIndex] = 20;
surface.YValues[lastIndex] = 20;
surface.ZValues[lastIndex] = 20;
Sure you can get a memory exception if you add a lot of data ...
Hope this helps - let us know if you have any questions.
Best Regards,
Nevron Support Team