Does this hold true for a 4 curve selection? So first curve slected is swept through 2 rails towards the opposite 4th curve in the selction? (So the only real determining factore of picking the curves would be the first one)

Hi Burr, no it doesn't really work like that for 4 curves - for a 4-curve Coons patch the curves are touching each other end to end forming a ring.

The ones opposite one another are not determined in that case by selection order, only by their relative placement in the ring which is a geometric arrangement, not a selection based one.

So like if you numbered the curves going around the ring like 1, 2, 3, 4 like this:



It pairs #1 and #3 opposite one another, and #2 and #4 as the other opposite pair.

In that case it is all determined by how the curves touch each other.

- Michael

Also in a Coons patch there is not exactly a "sweep" happening.

It's more like a Loft between the opposite pairs of curves, then those 2 lofts get combined together into a result surface.

There isn't really a sweep happening, it's more like a membrane attaching itself to all the curves.

There isn't one set that is the "profiles" and one set that is the "rails" for this particular kind of surface generation, they are all more being combined equally in a sense.

- Michael

Hi Anthony,

> It would be great for me and for other users
> to see precisely the workflow you've used to
> build the "boiteaproblem" :D
>I mean if you've got a bit of free time
> (I know it can be time consuming huhu)
> if you could take some screenshoot along the
> way it would be REALLY nice :D

I haven't forgotten, here is the run down for the body of the watch, I actually did this with a slightly different strategy than the previous model I did.

1. Line up the reference curves, I used the magenta line in the center to do this and place the center of the watch face on the origin,
it will be easier to work with.
Draw a circle around the outside (green) and use the second magenta line as reference to create the red profile curve, it's a simple line and arc.
Then transfer this red curve to the (top view) reference curves and orient the right way.


2. Revolve the red curve about the center to create a solid. (Construct > Revolve. with Cap ends)


3. Boolean difference so we just work with a quarter of the watch as it is symmetrical around the X and Y axis.
If you like there is a alternate Revolve script which allows you to revolve any angle segment, in this case 90°.


4. Draw the profile curves as shown with sharp corners, using the reference curves as a guide, join (Edit>Join) these curves together.
*Tip: if you are on V2 you can lock the reference curves so they don't get in the way or disturbed and still be used to snap to.


5. Draw an arc, (Draw Curve>Arc>3pts) as shown using the reference curves to snap to end points.
Make sure the curve is at the level shown in the second picture.


6. Draw a line (green) tangent to the inner curve of the reference as shown.
Again, make sure it is on the bottom level of the solid.


7. Extrude (Construct>Extrude) this line in Z+ (up) using the reference curves for the height.


8. Extrude the arc, but this time using the 'Set dir' button in the Extrude command and drag a construction line from
the middle of the bottom arc to the middle of the top arc of the watch to set the direction.
This surface should end up on a slight angle.


9. Select these two edges.


10. Create a blend (Construct>Blend) between the two surfaces and then join them (Edit>Join)


11. Now use the top curves, drawn previously, and the newly created surfaces to do a Boolean difference as show.
Hide or delete the pieces not needed.


12. Create a fillet on this edge first, I used 0.5


13. Select all these edges and create a 0.25 fillet.


14. Draw a line aligned with the top edge of the radius as shown.


15. Boolean difference the solid with this line and hide or delete the top part and line.


16. Mirror the quadrant through X and Y axis, then Boolean union the pieces together.
Done!


Cheers

Thanks so much Danny, for taking the time to explain your workflow - I'll definitely be saving this in my MoI tips and tricks document since once again I've gleaned insight on NURBS modeling techniques.
(Shame I've been ruined by poly modeling for so long...)

-Will

Superb and tricky tutorial!
Cool use of colors
Bravo!

PS You can find this tutorial in the French Section ;)