# Curve.PointAtParameter for Nurbs bug?

**URL:** <https://forum.dynamobim.com/t/curve-pointatparameter-for-nurbs-bug/91631>\
**Category:** Geometry\
**Tags:** dynamo\
**Created:** [July 10, 2023, 9:54am UTC](https://forum.dynamobim.com/t/curve-pointatparameter-for-nurbs-bug/91631 "2023-07-10T09:54:46Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![lazarica.tesu](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.dynamobim.com/lazarica.tesu/32/96056_2.png) [@lazarica.tesu](https://forum.dynamobim.com/u/lazarica.tesu)\
**Post date:** [July 10, 2023, 9:54am UTC](https://forum.dynamobim.com/t/curve-pointatparameter-for-nurbs-bug/91631/1 "2023-07-10T09:54:46Z")

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Hi,  
does anyone have an explanation why when using **Curve.PointAtParameter** on a nurbs curve the first point is placed with an offset? This happens both at the start and the end of the curve… and it makes no sense to me.

See attached photo for the result I was expecting, where I used a normal Line element and got a consistent distribution of points.

 ![image](https://us1.discourse-cdn.com/flex022/uploads/dynamobim/original/3X/d/b/dbffc248dcfdfedb61f97715d0b621e56ff8ffc5.png)

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**Author:** ![christian.stan](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.dynamobim.com/christian.stan/32/166296_2.png) [@christian.stan](https://forum.dynamobim.com/u/christian.stan)\
**Post date:** [July 10, 2023, 11:04am UTC](https://forum.dynamobim.com/t/curve-pointatparameter-for-nurbs-bug/91631/2 "2023-07-10T11:04:22Z")

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Hello,  
here may be a potential lead to your problem

 ![image](https://us1.discourse-cdn.com/flex022/uploads/dynamobim/original/3X/7/9/792f46fbaa5a13597d2ab9da40a0ac5412b6c450.png)

cordially  
christian.stan

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<div class="post-metadata">

**Author:** ![jacob.small](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.dynamobim.com/jacob.small/32/161030_2.png) [@jacob.small](https://forum.dynamobim.com/u/jacob.small)\
**Post date:** [July 10, 2023, 11:06am UTC](https://forum.dynamobim.com/t/curve-pointatparameter-for-nurbs-bug/91631/3 "2023-07-10T11:06:21Z")

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NURBS = Non Uniform Rational B-Spline. The non-Uniform aspect is the important bit.

Unlike uniform geometry (ie: a line) the formula defining any nurbs curve doesn’t have uniformly spaced parameters. I discussed this in some detail in a Dynamo office hour way back in like 2021: [08 - Computational Geometry: Model / Physical types​ with Dynamo - YouTube](https://youtu.be/ATAUp2Xr1h4?list=PLdlF7MirPEC2yNFTGymESd3t7Xosfk9c2&t=884)  
(time might be3 a bit off so check around that location).

You can also test this yourself using a NurbsCurve.ByPoints node where you use only 3 points and adjust the X and Y value of the middle point (keeping it between the start and end point).

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<div class="post-metadata">

**Author:** ![lazarica.tesu](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.dynamobim.com/lazarica.tesu/32/96056_2.png) [@lazarica.tesu](https://forum.dynamobim.com/u/lazarica.tesu)\
**Post date:** [July 10, 2023, 11:18am UTC](https://forum.dynamobim.com/t/curve-pointatparameter-for-nurbs-bug/91631/4 "2023-07-10T11:18:17Z")

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Thanks! This workaround works! 🥳

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<div class="post-metadata">

**Author:** ![lazarica.tesu](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.dynamobim.com/lazarica.tesu/32/96056_2.png) [@lazarica.tesu](https://forum.dynamobim.com/u/lazarica.tesu)\
**Post date:** [July 10, 2023, 11:20am UTC](https://forum.dynamobim.com/t/curve-pointatparameter-for-nurbs-bug/91631/5 "2023-07-10T11:20:11Z")

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It’s a bit more clear now 😄 thank you for the explanation!