Tween curve question.

Hello all.

I am having some problems with tween curve component.

Here is what I am trying to do.

1. Loft the cross-like crv with couple of standard circles. The loftting is going to be used as the base of paneling. Since paneling needs it to be one single srf, so I need this loft to be one single srf.

2. However, the cross-like crv is made up with multiple segments, (I could have rebuilt it, but it will give me too many control points) when I type "what" command in rhino, it tells me ,

Closed polycurve with 16 curve segments.

3. So, I need to make this cross-like crv into one NURBS crv. what I am doing now is, 'tween curve' between a standard circle and the cross-like crv.

Problems I am facing:

1: When I set "tween curve" f value to 1.0 and bake this curve, 'what' command, it tells me 16 segments. I am confused, it should be one segment, am I wrong?

2: When I set "tween curve" f value to 0.9--->bake--->what command, it tells me Closed NURBS curve. This is what I am looking for, except I want f value to be 1.

Attached is the .gh file.

Thank you for your help.

Attachments:

tween_crv_issue.gh, 10 KB

Replies to This Discussion

Permalink Reply by Jissi Choi on February 22, 2016 at 7:36pm

Because factor 1 means that the result only follows curve B ignoring curve A..

(0*A + 1*B)

check the help of Tween Curve..

F (Number) Tween factor (0.0=Curve A, 1.0=Curve B)

----

By the way, you can make your polyline as a periodic curve with 3rd degree by duplicating points at kinks..

But in this case, the loft result is not what you really want..

Furthermore the paneling must be with problems at kinks..

Permalink Reply by Bizkit on February 22, 2016 at 11:05pm

Hi Jissi

Thank you for the answer. I am wondering how to "make your polyline as a periodic curve with 3rd degree by duplicating points at kinks.."?

Permalink Reply by Jissi Choi on February 22, 2016 at 11:52pm

In the definition you've uploaded, the polyline is missing..

I'll edit the polyline if you upload your cross-like curve..

You need triply duplicated points at a kink in the 3rd degree curve..

Permalink Reply by Bizkit on February 23, 2016 at 1:30am

Hi Jissi

Here is the crvs. It was internalised into the .gh file, however, when I try to open the uploaded .gh, it crashes.

Attachments:

cross.3dm, 33 KB

Permalink Reply by Jissi Choi on February 23, 2016 at 8:29pm

First of all, you have joined curves with multiple degrees..

There are 3 & 5 degrees..

In this case, the lofted surface must be polysurface..

So, I have split your curve at kinks to 8 segments..

and rebuilt them with 3 degree..

Because 3 duplicated points are needed at kinks in 3 degree curve,

I have duplicated the start point of each curve.. and merged them in one list..

Then.. I have made a Nurbs curve with 3 degree..

Check the result..

It's a single surface..

Attachments:

cross-rebuild.gh, 17 KB

Permalink Reply by Bizkit on February 24, 2016 at 7:43pm

Hi Jissi

Wow, you blow my mind. Thank you so much for looking into this and the super detailed explanation. Now I know what is my problem. Knowing very little about NURBS.

Thank you again.

Permalink Reply by Bizkit on February 24, 2016 at 7:44pm

GH community really rocks.

Thanks again.

Permalink Reply by Bizkit on February 24, 2016 at 10:46pm

Hello

I have one more question.

On the first image you uploaded. The one getting the degree of the crvs. Could you please let me know why did you use subtraction? for the second subtraction why did you put number "1". Was it because of "The knots are a list of (degree+N-1) numbers"?

Permalink Reply by Jissi Choi on February 25, 2016 at 10:55pm

Yes..

Check this brief article..

http://www.rhino3d.com/nurbs/

The knots are a list of (degree+N-1) numbers, where N is the number of control points.

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