Flip Surface (Not Brep, Untrimmed single surface)

I just want to make surface flip normal , but Surface class do not have Flip() method.

How can I flip “Surface”(Untrimmed single surface) instance ?

I tried this. But it didn’t work.

    private Surface FlipSurfaceNormal(Surface surface)
    {
        var brep = surface.ToBrep();
        if (brep == null || brep.Faces.Count == 0)
        {
            RhinoApp.WriteLine("Error");
            return surface;
        }

        brep.Flip();

        var flippedSurface = brep.Surfaces[0];
        return flippedSurface;
    }

Flipping a brep just toggles the reverse flags on the faces. The underlying surface is unchanged. I think you’re looking for Surface.Transpose.

1 Like

Thank you.
Yes, Transpose can reverse normal as a result of exchange U and V.
But I want to change only N, don’t wanna change UV.

In “Dir” command, we can change only normal direction of a surface.

How “Dir” can change only direction of a single surface?
Are there any API method to flip only Normal of a single surface ?

Dir changes the normal by toggling that reverse flag. The surface in the document is a brep with a single face.