Hi Bob, well in your previous screenshot here: http://moi3d.com/forum/index.php?webtag=MOI&msg=7692.11 that definitely looked like you were clicking the points inside the "Left" viewport. Again, that's normal that you won't get an "On srf" snap in that view, as I tried to describe above.

In your new screenshot where you show it working ok, that looks like you are drawing in the 3D viewport there - and when you place the points in the 3D viewport that's when it should work.

I'm sorry but I can't repeat any unusual behavior with your model over here - but definitely some of the screenshots you have shown above the problem is that you were picking the points in the Front or Top views and in those views "on srf" snap will not be active by default which is normal behavior.

You should be able to repeat this with your model - load the model and then maximize the 3D view. Now draw a rectangle - you will see "on srf" work for the first point picked. If you then switch to maximize the Top view and try it, you won't get any "on srf" snap in that view because by default "on srf" is suppressed in any of the Top, Front, or Right views...

> Any ideas on why things seem to work better when the model is moved?

Well, if you move the model to the world origin, the grid planes for the Top, Front, or Right views will more closely coincide with the model and so when you draw on those view's grid planes it won't be so far away from your model.

- Michael