Hi McNeel
I’d love for the “End Analysis”-feature of “Closed crv seams” visibility to be incorporated in the “Turn on control points when selecting a curve…”-feature. OK, that sentence made almost no sense, even to me…
It would be nice if the seam of a closed curve was differentiated from the other control points, when you select a closed curve - just like it is in the End Analysis panel, where they are pink. Especially since Rhino can sometimes be a little finicky when it comes to seam positions.
Regards, Jakob
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I was thinking recently that this would be pretty handy - it would also be really nice if the end points had different colours so you could tell the direction of the curve quickly
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to clarify, you want the point that makes up the seam of a closed curve to be differentiated by color when control points are active.
do I have that right?
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closed Curve, Degree 3, 6 cv’s
pink = End/Start Point
blue line shortest Distance from “first” CV (perpendicular) to Curve.
how would that apply to above curve ?
do i miss something ? can i learn something ?
Am I an
cheers - tom
Hi @theoutside
Yes, exactly. Or at least displayed - but yes, preferably in another colour so that it’s easier to differentiate.
-Jakob
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Hi @Tom_P
By no means did you miss anything. My initial description was just really bad 
I’m basically looking for the seam to display alongside the controlpoints upon selection of a curve - without having to run the ShowEnds or CrvSeam. Mainly for visual confirmation of the seam, so that I can move it - if needed - before building a surface from it, eg. lofts consisting of multiple closed curves. I find myself having to go back and move the seams a lot. Preferably a switch somewhere in settings, so that people who have no use/interest in the seam don’t have to deal with it.
Sorry for any confusion!
-Jakob
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… just wanted to point out that Curve End is not always identical with a CV. (EDIT: ) for closed Curves.
I would appreciate a more advanced Curve-Display:
CVs, Knots, Endpoints, Seams, Inclination Points, …
there was a Feature-request / wish about Midpoint display somewhere…
would be nice to have a “advanced Curve Display” Analysing
- and it would be nice if those Analysing tool would have an automatic add all Curves / Objects Option - including a limitation to a Layer. (advanced Display for all Curves on a bunch of selected Layers)
have a nice day - cheers - tom
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Every NURBS curve has a CV both ends.
Apart from that, Rhino has all information about curves and surfaces available “under the hood”; that information should be displayable at the user’s demand, on a per-curve or per-surface basis, and persistently so, until no longer needed, just like Alias, Catia, or ICEM allow since like forever.
i was talking about a closed curve - updated my post.
you can set the knot vector different then fully multiply (for first/last) for an open curve so it will not start with the CV.
In general closed NURBS curves in Rhino do not have a control point on the curve at the ends/seam of the curve. Very simple examples:
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Very odd. Here, in Rhino 8 macOS, I have the first/last CV on the closed curve (degree 5/4 spans), where I would expect it to be.
Hi Jakob -
I’ve written that up as RH-90354 Display: Differentiate First and Last Control Point from Rest
-wim
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@wim The title of the YT item is misleading. It should include displaying the seam of a closed curve, as the seam may not coincide with any control points.
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The title corresponds with the contents of that YT.
Here’s a different one that you might like better.
→ RH-90360 Display: Closed Curve Seam Point
-wim
That YT is not only about differntiating the first and last control points. It includes:
The user would like to immediately see where the seam of the curve is located and requests that the (coinciding) first and last control points are drawn in a different color.
The seam does not always coincide with the first and last control points. Differentiating the first and last control points may not show where the seam is located.
There are different ways to create a “closed” curve in Rhino.
Some methods usually result in no control points located on the curve. (“Usually” because there are special cases with control points on the curve: if there are a sufficient number of control points along a line for example.) These curves the same inherent continuity across the seam as the continuity between spans of a multi-span curve of the same degree (C2 for a degree 3 curve, C4 for a degree 5 curve, etc). That continuity across the seam is independent of control point location. Rhino identifies these as periodic curves, even though they can have arbitrary shape. (“Periodic” refers to the data used internally for calculations.)
Examples of such methods include:
- Use
Curvewith PersistentClose=Yes . - Use
Curvewith PersistantClose=No and place the last control point at the same location as the first control point while creating the curve - Use
InterpCrvand select the location of the last interpolation point to be the location of the first interpolation point - Use
CurveThroughPtwith Closed=Yes
Other methods result in a control point located at the seam. These closed curves will have only inherent C0 (position) continuity across the seam. There may be higher level continuity across the seam depending on the position of other control points.
One method to create such a close curve is:
- Create an open curve. After the open curve is created, move/drag one end control point of the open curve to coincide with the other end control point. The result will be a closed curve with a control point at the seam, and only C0 continuity across the seam.
RH-90364 Improved curve point UI