Wish : Volume calculation of vdGroundSurface object

/// <summary>
/// Calculate the volume of the collection sliced portion, using a plane from the passed parameters.
/// </summary>
/// <param name="origin">A point needed to determine the slice plane.</param>
/// <param name="direction">A Vector that is perpendicular to the plane and specifies the direction of the visible portion of the gTriangles.</param>
/// <returns>The volume of the sliced collection portion.</returns>
public double Volume(gPoint origin, Vector direction)

and can be used as following to a vdGroundSurface object :

vdGroundSurface gsurf = new vdGroundSurface();
gsurf.SetUnRegisterDocument(vdFramedControl.BaseControl.ActiveDocument);
gsurf.setDocumentDefaults();
//Fill Points Here
gsurf.Triangles.Volume(new gPoint(0, 0, 0), new Vector());

In the following picture in order to compute the volume above the blue plane we simply call the Volume method of the vdGroundSurface's triangles passing a point and a Vector that determine this Blue plane.