# GeomAbs_SurfaceForm.hxx File Reference

`#include <Standard_PrimitiveTypes.hxx>`

## Enumerations

enum | GeomAbs_SurfaceForm { GeomAbs_PlanarForm, GeomAbs_ConicalForm, GeomAbs_CylindricalForm, GeomAbs_ToroidalForm, GeomAbs_SphericalForm, GeomAbs_RevolutionForm, GeomAbs_RuledForm, GeomAbs_QuadricForm, GeomAbs_OtherSurfaceForm }

Provides information about the continuity of a curve:
- C0: only geometric continuity.
- G1: for each point on the curve, the tangent vectors
"on the right" and "on the left" are collinear with the same orientation.
- C1: continuity of the first derivative. The "C1" curve is
also "G1" but, in addition, the tangent vectors " on the <br> right" and "on the left" are equal.
- G2: for each point on the curve, the normalized
normal vectors "on the right" and "on the left" are equal.
- C2: continuity of the second derivative.
- C3: continuity of the third derivative.
- CN: continuity of the N-th derivative, whatever is the
value given for N (infinite order of continuity).
Also provides information about the continuity of a surface:
- C0: only geometric continuity.
- C1: continuity of the first derivatives; any
isoparametric (in U or V) of a surface "C1" is also "C1".
- G2: for BSpline curves only; "on the right" and "on the <br> left" of a knot the computation of the "main curvature <br> radii" and the "main directions" (when they exist) gives the same result.
- C2: continuity of the second derivative.
- C3: continuity of the third derivative.
- CN: continuity of any N-th derivative, whatever is the
value given for N (infinite order of continuity).
We may also say that a surface is "Ci" in u, and "Cj" in v
to indicate the continuity of its derivatives up to the order
i in the u parametric direction, and j in the v parametric direction.
. More...

## Enumeration Type Documentation

enum GeomAbs_SurfaceForm

Enumeration values:

  GeomAbs_PlanarForm |
  GeomAbs_ConicalForm |
  GeomAbs_CylindricalForm |
  GeomAbs_ToroidalForm |
  GeomAbs_SphericalForm |
  GeomAbs_RevolutionForm |
  GeomAbs_RuledForm |
  GeomAbs_QuadricForm |
  GeomAbs_OtherSurfaceForm |