About Datum Visibility in Project Views

When you resize model (3D) datum extents, you can control in which view they are visible.

Video: Control Visibility Datums

If the datum planes do not intersect the view plane, they are not visible in the view.

Note: A datum will not display if it falls outside of the crop region of the view. If the datum is set to display 2D extents and then it is cropped out of the view by enabling the crop region, the location and length of the datum are not remembered. Therefore, when the crop region is disabled in the view (so everything in the view displays), the datum will become visible again, but it will display its 3D extents, instead of its original 2D extents.

In the following example, the top level line is not visible in the section view, because its model (3D) extents do not intersect it.

In the next example, the grid is visible only in the first 2 plan views, because its model (3D) extents do not intersect the third level line.

You may notice a datum intersecting a view plane but not displaying in the view. If you select the datum, you will notice that its view-specific extent intersects the view plane, but not its model extent, as the next figure shows. The open circle in the figure shows the 3D model extent, which is not intersecting the section. The filled circle is showing the 2D extent, which has intersected the section. As a result, Level 3 will not display in the section view.