Hello Experts. When i use PlanarSRF to create a surface out of these curves it changes the control points of the original curve to that of an invisible rectangular curve. is there a way where i can get the control points back to the blue place?
The four “rectangular” contorl points are the control points of the surface, not the curve. The curve continues to exist (unless you deleted it) unchanged by PlanarSrf. The curved edge of the surface along the curve is a trimmed edge.
Surfaces can have untrimmed edges or trimmed edges. When a surface is trimmed, the control points of the surface are not changed. Internal trim curves are created and the portion of the surface which is inside the trim curves is used for geometry and is visible to the user. The trim curves are not directly accessible using Rhino commands. In this particular situation the trim curve coincides with an input curve but is distinct from the input curve.
PlanarSrf creates a rectangular planar surface which fits all the input planar curves, and then trims the planar surface to the input curves.
Use EdgeSrf to create an untrimmed surface with edges matching two, three or four curves.