CreateCutPlaneSolid.cs

public static Autodesk.DesignScript.Geometry.Solid CreateCutPlaneSolid(global::Revit.Elements.Element planv)
        {

            View planView = planv.InternalElement as View;
            BoundingBoxXYZ bbActiview = planView.get_BoundingBox(null);
            Plane planePlanView = planView.SketchPlane.GetPlane();
            PlanViewRange viewRange = (planView as ViewPlan).GetViewRange();
            double cutPlaneHeight = viewRange.GetOffset(PlanViewPlane.CutPlane);

            XYZ pt0 = new XYZ(bbActiview.Min.X, bbActiview.Min.Y, bbActiview.Min.Z);
            XYZ pt1 = new XYZ(bbActiview.Max.X, bbActiview.Min.Y, bbActiview.Min.Z);
            XYZ pt2 = new XYZ(bbActiview.Max.X, bbActiview.Max.Y, bbActiview.Min.Z);
            XYZ pt3 = new XYZ(bbActiview.Min.X, bbActiview.Max.Y, bbActiview.Min.Z);

            XYZ pt00 = ProjectOnto(planePlanView, pt0);
            XYZ pt11 = ProjectOnto(planePlanView, pt1);
            XYZ pt22 = ProjectOnto(planePlanView, pt2);
            XYZ pt33 = ProjectOnto(planePlanView, pt3);

            Line edge00 = Line.CreateBound(pt00, pt11);
            Line edge11 = Line.CreateBound(pt11, pt22);
            Line edge22 = Line.CreateBound(pt22, pt33);
            Line edge33 = Line.CreateBound(pt33, pt00);

            List<Curve> edges0 = new List<Curve>();
            edges0.Add(edge00);
            edges0.Add(edge11);
            edges0.Add(edge22);
            edges0.Add(edge33);

            CurveLoop baseLoop0 = CurveLoop.Create(edges0);
            List<CurveLoop> loopList0 = new List<CurveLoop>();
            loopList0.Add(baseLoop0);
            Solid preTransformSolid =
                GeometryCreationUtilities.CreateExtrusionGeometry(loopList0,
                    XYZ.BasisZ, cutPlaneHeight);
                    //transform
            Solid transformSolid = SolidUtils.CreateTransformed(preTransformSolid,
                bbActiview.Transform);

            return transformSolid.ToProtoType();
        }
        [IsVisibleInDynamoLibrary(false)]
        public static XYZ ProjectOnto(this Plane plane, XYZ p)
        {
            double d = plane.SignedDistanceTo(p);
            XYZ q = p - d * plane.Normal;

            return q;
        }