Irregular3DSet Appearance , dedicated contour widget

Dear Bill,

Please find attached a picture showing the Contour widget of two different
data sets. As you could notice the data shown are identical just the window
with girded 3D set can have filled contours, while the irregular 3D set is
not reacting using the contour widget to fill the contours.

Is this normal, or it is possible that Irregular3DSet is displayed in the
same way as the regular 3D grid set.

Thanks in advance for your comments.

With best regards, Dean.

Attachment: contour.GIF
Description: GIF image