ST_ControlPoints — Returns the control points of a NURBS curve as a MULTIPOINT geometry.
geometry ST_ControlPoints(geometry nurbscurve);
Extracts the control points from a NURBS curve and returns them as a MULTIPOINT geometry. Control points define the control polygon that influences the shape of the NURBS curve.
The function raises an error if the input is not a NURBS curve. Returns NULL if the input is NULL.
Availability: 3.7.0
-- Extract control points from a NURBS curve
SELECT ST_AsText(ST_ControlPoints('NURBSCURVE(2, (0 0, 5 10, 10 0))'::geometry));
-- Result: MULTIPOINT((0 0),(5 10),(10 0))
-- Count the number of control points
SELECT ST_NPoints(ST_ControlPoints('NURBSCURVE(2, (0 0, 5 10, 10 0))'::geometry));
-- Result: 3