The Old "Hole in a Curved Surface" Issue...

This is kind of a help/bug/feature-request post all in one... wasn't sure which forum section to put it in.

So, first, I understand that SUB-D modelling and punching a perfectly circular hole in a curved surface, whilst maintaining good edge flow, and perfectly maintaining the curvature of said surface, is one of those classic issues where NURBS-based modellers/CAD have the upper hand.  Yes, there's boolean subtraction, but that can create some pretty messy geometry.  There are some other manual methods that I've had ok luck with in NVIL, but none of which did exactly what I wanted.  I wish there was a way I could use a really slick method like one that MODO users have access to per the following short youtube video: http://www.youtube.com/watch?v=7Z3shqwnGoE .

The video is divided into 2 sections... one is a method of creating nice holes in a flat surface, the other uses a similar method by applying it to a curved surface.  Well, the second method can't be done if the first method can't be accomplished, so I tried it in NVIL and ran straight into a brick wall.  What I attempted to do was the following: 

1. Create a plane with multiple subdivisions and delete several polygons in the centre.
2. Create a cylinder with X number of slices... in this case 48 or some other arbitrarily high number.
3.  Turn on RETOPO mode and set the cylinder as a snapping reference.
4.  Grab the inside edge vertices of the plane and attempt to scale them along the XZ plane until they snap to the cylinder, leaving the verts in a nicely circular array.  I tried doing this in several ways (including scaling options such as AXIS scale), and using various views including side and top ortho.  Everything fell apart at this stage.  For one, it appears that there's no way I can lock the scaling to the ZX plane - as soon as the verts got near to the retopo reference mesh, they started moving in the Y direction, etc.  Also, there was no way to keep back-facing verts (relative to the current camera view) from popping through the back side of the reference mesh and snapping to the front.
5.  Obviously, with the above issues, it would not be possible to continue forward to the second half of the youtube video where we are performing similar operation on a curved surface instead of a plane.

Attached are some images that should help describe what I'm on about....

Thanks,
Jonny

Rewatching the video above a couple of times, it looks like Modo's key feature in this operation is the "Background Constraint", which I'm guessing means it constrains vertex movements to conform to background/deselected meshes... kind of like the retopo reference meshes in NVIL, but not quite.  Is there any way to enable a similar "Background Constraint" in NVIL at present?  Check out the area of the video above at around 5:20.

You can either use "Circularize" or "Align-> Cylinder" to create the circle.
"Circularize" also functions on curved surfaces(maintains curvature), although I have not made many tests on that particular option/function.

"Circularize" is a basic streamline tool. You can find it(and add a hotkey) in "Edit-> Customize-> Streamline tools"-> "Streamline basic tools-> Subobject tools-> Mixed tools-> Circularize_selection"

Thanks Steve!  I was already aware of spherize, but circularize is much more the ticket in this kind of situation, it appears.  For other reasons, but as a separate issue, I'd still find it handy to have a "Background Constraints" option.  However, for the specific task of cutting holes, circularise is very quick and handy indeed.

Ok, here's an update.  I've been playing with Circularize, and I can't get the circle to follow the curvature of a curved surface.  Every time I use circularize, it creates a planar circle on, I presume, a plane aligned along the subobject normals of the selection being circularized.  Here is an example where I made a smooth surface from an extruded spline, made a local subdivision at a curved area to create greater poly density in the area, and the Circularized a selection of vertices contained within.  You can see from the 3rd section of my screenshot, that when viewed directly from above, the circularized section does not follow the curvature of the surface.  Any thoughts of how to make that happen?  In the Modo vid I referenced above, one would have to create a duplicate of the original curved surface prior to being circularized, then once the Circularize operation had been performed, the vertices could be made to conform to the duplicate mesh.

To perform circularize on the surface and keep it to curvature, you will need to perform the circularize before you delete the polygons (that are inside the hole you are creating), so that there is geometry for the function to follow.
Select the border edges of those polygons(that you will be deleting), perform circularize and while the tool is still active, tap the "caps lock" which toggles the surface type of circularize.

If it does not give a good result, you will need to follow a similar path as shown in the vid you linked to. You can create a second copy(of the original surface) and use "Surface alignment" after creating the hole with "circularize".

I really appreciate the help.  The Capslock tap was all it took.  Now that you've shown me how to use it properly, the circularize tool is a thing of beauty - much faster than the modo method, and I'll no doubt be using it *a lot*.   

Just a bit of fun. Sphere with 24(round) holes.