When using higher order elements as in Howto create higher order elements?, are the elements truely second order and the node positions are corrected for the curvature of the surface, or are the node positions derived from simply adding midpoint nodes?
The nodes are snapped to boundary for both surfaces and curves.
The first case shows spline surface with linear elements.
The second case uses quadratic elements. The faceting on this coarse mesh is a bit odd due to snapping the nodes to the surface.
The same result is clearly visible on the curves with the planar circle below.
To add to @karl’s answer, you can control whether Cubit projects mid-nodes to surfaces in the Options dialog found under the Tools menu bar:
The default setting is “smart”, which will avoid projecting mid-side nodes if it would result in a poor quality (e.g. inverted) element. You can also set this value with the command:
set node constraint [on | off | smart]