Mea Culpa. This is our fault. This capability does not exist for 3d contours and neither the Use Polygon or the Draw Polygon controls should be visible in the 3d contour dialog box.
You can modify the grid limits so constrain the extent of your 3d contours. Go to the Grid tab in the 3d Contour dialog box. Then either manually change the maximum or minimum values defining the grid or click on the Draw Grid button and click on the corners of the grid that will limit the extent of the 3d contours. bljacobs
