# Feature Request: Curve Through Interpolated Points

**URL:** <https://discourse.mcneel.com/t/feature-request-curve-through-interpolated-points/125479>\
**Category:** Rhino for Mac\
**Created:** [June 7, 2021, 1:53am UTC](https://discourse.mcneel.com/t/feature-request-curve-through-interpolated-points/125479 "2021-06-07T01:53:55Z")\
**Posts on this page:** 9\
**Page:** 1

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**Author:** ![miano](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/miano/32/762004_2.png) [@miano](https://discourse.mcneel.com/u/miano)\
**Post date:** [June 7, 2021, 1:53am UTC](https://discourse.mcneel.com/t/feature-request-curve-through-interpolated-points/125479/1 "2021-06-07T01:53:55Z")

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If I have:

1. Two curves that are not connected.
2. A set of points located between the two curves with one point located the end of each curve

And I Curve Through Interpolated Points to join the curve through the points and while specifying Start or End Tangent, I wish Rhino would ignore the point at the end for the purpose of the tangent.

It is hit or miss whether Rhino locks on to the point (meaningless result) or the end of the curve.

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**Author:** ![wim](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/wim/32/747482_2.png) [@wim](https://discourse.mcneel.com/u/wim)\
**Post date:** [June 7, 2021, 8:14am UTC](https://discourse.mcneel.com/t/feature-request-curve-through-interpolated-points/125479/2 "2021-06-07T08:14:54Z")

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Hi -

> [@miano](#):
>
> It is hit or miss whether Rhino locks on to the point (meaningless result) or the end of the curve.

That seems to behave as expected here in a quick test - or I am completely misunderstanding the issue here. Can you post a simple file?  
-wim

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<div class="post-metadata">

**Author:** ![miano](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/miano/32/762004_2.png) [@miano](https://discourse.mcneel.com/u/miano)\
**Post date:** [June 8, 2021, 2:37am UTC](https://discourse.mcneel.com/t/feature-request-curve-through-interpolated-points/125479/3 "2021-06-08T02:37:48Z")

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An illustration:

1. I start with two lines and three points. Two of the points are at the end of a line.
2. I copy and delete the two points at the end of the line.
3. I draw a curve through interpolated points using the start and end tangents on both.

If there is no point at the end of the line, I consistently get the curve tangent to the line.

If there is a point at the of the line, I more often than not get a curve that is not tangent to the line. It appears that the N/T opens lock on the to the point, rather than the line.

 ![Screen Shot 2021-06-07 at 10.33.17 PM](https://global.discourse-cdn.com/mcneel/uploads/default/original/4X/1/7/5/17512d361ac0dd6cc5e5b1d69b9b7f8d392d9042.png)  
[Problem Curve.zip](https://discourse.mcneel.com/uploads/short-url/2fSJKVVviccWtpMjlXitmIpMihl.zip) (7.7 KB)

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<div class="post-metadata">

**Author:** ![wim](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/wim/32/747482_2.png) [@wim](https://discourse.mcneel.com/u/wim)\
**Post date:** [June 8, 2021, 9:24am UTC](https://discourse.mcneel.com/t/feature-request-curve-through-interpolated-points/125479/4 "2021-06-08T09:24:39Z")

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Hi -

> [@miano](#):
>
> If there is a point at the of the line, I more often than not get a curve that is not tangent to the line. It appears that the N/T opens lock on the to the point, rather than the line.

I’m not sure how you are getting that non-tangent curve. This is what I do:  
 ![2021-06-02 Tangent InterpCrv](https://global.discourse-cdn.com/mcneel/uploads/default/original/4X/9/1/5/9150d0837980e57c1081ce1eecdb6354aea392e9.gif)

-wim

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<div class="post-metadata">

**Author:** ![davidcockey](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/davidcockey/32/771921_2.png) [@davidcockey](https://discourse.mcneel.com/u/davidcockey)\
**Post date:** [June 8, 2021, 11:22am UTC](https://discourse.mcneel.com/t/feature-request-curve-through-interpolated-points/125479/5 "2021-06-08T11:22:27Z")

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Is this the difference between InterpCrv with Knots=Uniform vs Knots=Chord?  
I am assuming InterpCrv in Rhino for Mac has the same options as in Rhino for Windows

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<div class="post-metadata">

**Author:** ![wim](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/wim/32/747482_2.png) [@wim](https://discourse.mcneel.com/u/wim)\
**Post date:** [June 8, 2021, 2:14pm UTC](https://discourse.mcneel.com/t/feature-request-curve-through-interpolated-points/125479/6 "2021-06-08T14:14:56Z")

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Hi David -

> [@davidcockey](#):
>
> Is this the difference between InterpCrv with Knots=Uniform vs Knots=Chord?

It doesn’t look like that in this case, no. With either of those, the resulting curve is tangent to the lines.  
-wim

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<div class="post-metadata">

**Author:** ![miano](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/miano/32/762004_2.png) [@miano](https://discourse.mcneel.com/u/miano)\
**Post date:** [June 8, 2021, 2:16pm UTC](https://discourse.mcneel.com/t/feature-request-curve-through-interpolated-points/125479/7 "2021-06-08T14:16:49Z")

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No, Both are with knots=chord.

The issue is the T/N options (tangents) that seem to lock on to the point rather than the line (or any other type of curve).

Sometimes, the curve will turn out tangent to the line but it is random.

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<div class="post-metadata">

**Author:** ![wim](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/wim/32/747482_2.png) [@wim](https://discourse.mcneel.com/u/wim)\
**Post date:** [June 8, 2021, 2:20pm UTC](https://discourse.mcneel.com/t/feature-request-curve-through-interpolated-points/125479/8 "2021-06-08T14:20:28Z")

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> [@miano](#):
>
> The issue is the T/N options (tangents) that seem to lock on to the point rather than the line (or any other type of curve).

For curves that are not lines, you’ll either need to turn the points of that curve on or have construction geometry. You need to place the tangent point in the correct direction.  
-wim

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<div class="post-metadata">

**Author:** ![miano](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/miano/32/762004_2.png) [@miano](https://discourse.mcneel.com/u/miano)\
**Post date:** [June 8, 2021, 2:34pm UTC](https://discourse.mcneel.com/t/feature-request-curve-through-interpolated-points/125479/9 "2021-06-08T14:34:42Z")

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If I don’t have a point at the end of the start/end curve, with the T/N option I get tangent indicator that is fixed along the tanget.

 ![Screen Shot 2021-06-08 at 10.27.16 AM](https://global.discourse-cdn.com/mcneel/uploads/default/original/4X/9/7/1/971a251ed2d3577d642ca576d929334278095fa6.png)

If I have a point at the end of the line, the tangent indicator will move in any direction (most of the time).

 ![Screen Shot 2021-06-08 at 10.31.31 AM](https://global.discourse-cdn.com/mcneel/uploads/default/original/4X/1/f/5/1f5e03d71908c97bf5498019d6c99d89f0fd7366.png)

My observation is that sometimes tangent locks on to the end of the line (correct result) and sometimes locks on to the point (the tangent line can go anywhere).