issurfaceinplane

          
using System.Linq;
using Rhino;
using Rhino.DocObjects;
using Rhino.Geometry;
using Rhino.Commands;
using Rhino.Input;

namespace examples_cs
{
  public class IsPlanarSurfaceInPlaneCommand : Command
  {
    public override string EnglishName { get { return "csIsPlanarSurfaceInPlane"; } }

    protected override Result RunCommand(RhinoDoc doc, RunMode mode)
    {
      ObjRef obj_ref;
      var rc = RhinoGet.GetOneObject("select surface", true, ObjectType.Surface, out obj_ref);
      if (rc != Result.Success)
        return rc;
      var surface = obj_ref.Surface();

      Point3d[] corners;
      rc = RhinoGet.GetRectangle(out corners);
      if (rc != Result.Success)
        return rc;

      var plane = new Plane(corners[0], corners[1], corners[2]);

      var is_or_isnt = "";
      if (IsSurfaceInPlane(surface, plane, doc.ModelAbsoluteTolerance))
        is_or_isnt = " not ";

      RhinoApp.WriteLine("Surface is{0} in plane.", is_or_isnt);
      return Result.Success;
    }

    private bool IsSurfaceInPlane(Surface surface, Plane plane, double tolerance)
    {
      if (!surface.IsPlanar(tolerance))
        return false;
     
      var bbox = surface.GetBoundingBox(true);
      return bbox.GetCorners().All(
        corner => System.Math.Abs(plane.DistanceTo(corner)) <= tolerance);
    }
  }
}