I was pondering this for a second.

What if I have a Nurbs curve that I convert to a Polygon based on Hulls? Can I then have that converted polygon's UV attributes transferred back to a newly reconverted NURBS curve that was generated from that poly curve?

In other words:
1) Draw a NURBS curve
2) Convert to Polygon based on Hulls
2.5) Facet/Fuse the Polygon as UNIQUE Points
3) transfer UV Attributes from NURBS curve to Poly based on Hulls.
4) Convert Polygon based on Hulls back to a NURBS Curve

—–

What I am hoping this process will produce is a set of NURBS Curves that are divided according to Hulls. This will enable me to Carve precisely at Nurbs Control Vertices that lie on the curve (In Maya these would be Edit Points instead of CV's).

Any thoughts?

Thanks in advance, markerline

You can use AttribTransferCurve SOP to do that:
http://www.orbolt.com/asset/animatrix::attribCurveTransfer::1.00 [orbolt.com]

This works a lot better for curves than using AttribTransfer SOP which only factors proximity, not a 1:1 mapping along the curves.

I'm trying to apply your tool but I'm not sure I'm doing it right. I end up with unfinished line segments in the order of 2, rather than individualized curved NURBS segments in the order of 4.

You need to apply the transfer before splitting your curve into multiple pieces. When you split it afterwards for instance using the Carve SOP, the attributes should be transferred correctly.

Can you explain how to achieve what I would like to? I don't follow how to apply the transfer before breaking up the curve, since the broken pieces would give me the number of primitives I need. I can see that I would be transferring the uv attributes of the original curve, but maybe you can base an explanation around some of what was posted in the last part of this thread:

http://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&t=29332&highlight= [sidefx.com]

Sorry I got confused. In your case, you have multiple NURBS curves created from the segments of the original curve where you want the points to have 0-1 UV values?

If you can post an example, that would also be useful. I think if you split the curve using Carve and then convert to NURBS using hulls, you would be able to transfer the values much easily.

What I essentially and ideally would like is for an order 4 NURBS curve to have points that reside on the curve itself, rather than control vertices that lie off in space away from the curve, and use these resident points to carve AT those points precisely.

In Maya as explained before you can use Edit Points which reside on the curve but are typically not used to edit the curve appearance (that is reserved for control vertices or CVs) and Cut the Curve at those edit points. This gives precise control when desiring to skin between curve/line segments that have been formed from a closed 2D or 3D surface.

You can create curves with Breakpoints. These are knots/grevel points that lie directly on the NURBs curve.

To edit breakpoints on NURBs curves, you need to turn on the display of Breakpoints in the Display Options dialog. This option isn't added to the right hand display strip at this time. Breakpoints can be edited and snapped to anything. To insert new knots, you can use the Refine SOP.

To carve or cut your curve directly on these breakpoints, use the Cave SOP and set First and Second U then enable the Breakpoints radio folder and toggle on “Cut At All Internal U Breakpoints”.

As for the uv's, if you apply your base uv's to the original NURBs curve, the uv's will ride along for free. They even properly interpolate with the Carve SOP all the way to the conversion of Polygons. That would be the “Houdini” way.

Actually this automatic handling of the attributes seems to be a unique behaviour compared to all the other software out there. Us Houdini users take this for granted.

The rule is no SOP should destroy attributes as it does it's work. Within reason.

Jeff. I couldn't thank you more. I've been using Carve for a very very long time and I never explored the breakpoints option as I never really learned how it is used (when someone showed me the carve sop years ago). This is a perfect and elegant solution and saves me lots of resources by forgoing the need to invest in a Maya license just for the sake of an important tool in my workflow: The tool already exists in Houdini! GREAT!!!

Houdini actually has a decent NURBs/Bezier toolkit. Please ask away as you hit these issues.