A little demo of what the new "Align to surface" option in Array curve can do now.

Here is a curve that has been projected on to a surface, and a cylinder that has been drawn aligned to the surface normal at the start of the curve:



With the regular array curve, you can replicate that cylinder along the curve, but it will have a general gradual rotation applied to it, which will not necessarily keep it aligned with the surface normal at all points:



Notice there especially towards the end, it is not very close at all to the surface normal anymore, it just does not know anything about the surface so it does not take it specifically into account.

However, there is now a new "Align to surface" button in the options for array curve, here:




If you push that, you will be able to pick a surface and that will inform array curve that you want to maintain alignment to the surface normal of that surface. When this is engaged, array curve will incorporate an additional rotation into each array instance, to keep it relative to the surface normal at that point, to get this result:




To have everything in the final result aligned to follow right along the surface normal, you do need to have the initial item already placed in alignment to the surface normal at the starting point of the array though. In the future at some point it would probably be good to have a sort of "auto place" mechanism for this similar to the auto-place mode for sweeps, so that you could have an initial object located flat in world coordinates and have it moved into place for you.

- Michael