Hello chenz,
progeCAD "surface" entities use a much older, simpler basis for 3D design in progeCAD created with empty
wireframe.
Wireframe constructions has its primary use in creating 3D architectural and landscape mockups of great complexity but lacking detailed accuracy - (especially in curvature approximations) mainly for depiction and rendering/presentation purposes.
Starting with
AutoCAD R13, Autodesk began to license the NURBs-based
3D solid modeling kernel ACIS from Spatial (now part of Dassault) for creating manufacturable 3D parts that were more accurate -especially when designing complex surface curvatures. progeCAD has similarly offered both systems of 3D design in progeCAD Professional for several years now.
We have had several requests for a 3D tutorial and are currently working on one for progeCAD.