# Why doesn't grasshopper shatter at the specified point?

**URL:** <https://discourse.mcneel.com/t/why-doesnt-grasshopper-shatter-at-the-specified-point/149588>\
**Category:** Grasshopper\
**Tags:** windows, rhino7\
**Created:** [October 24, 2022, 11:39am UTC](https://discourse.mcneel.com/t/why-doesnt-grasshopper-shatter-at-the-specified-point/149588 "2022-10-24T11:39:44Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Plamen\_Panchev](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/plamen_panchev/32/347478_2.png) [@Plamen\_Panchev](https://discourse.mcneel.com/u/Plamen_Panchev)\
**Post date:** [October 24, 2022, 11:39am UTC](https://discourse.mcneel.com/t/why-doesnt-grasshopper-shatter-at-the-specified-point/149588/1 "2022-10-24T11:39:44Z")

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I have this simple curve and I’m trying to split it at the point. The problem is that when I’m using the shatter command it doesn’t actually split it at the point, but at some other random point near it. Any suggestions or alternatives on how to do this would be appreciated  
[Shatter problem.gh](https://discourse.mcneel.com/uploads/short-url/uHBHN31DGMmRkW8nzL2ChhjeHMM.gh) (17.6 KB)  
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**Author:** ![inno](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/inno/32/544036_2.png) [@inno](https://discourse.mcneel.com/u/inno)\
**Post date:** [October 24, 2022, 12:02pm UTC](https://discourse.mcneel.com/t/why-doesnt-grasshopper-shatter-at-the-specified-point/149588/2 "2022-10-24T12:02:46Z")

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shatter wants a parameter _t_ as a number, you’re feeding it point coordinates that get translated to numbers (not the same thing)

don’t know what is your final goal with this definition, but correcting those _t_ parameters is for sure an important thing to do 🙂

for instance here, if you want to shatter curve A based on the point in B:

 ![image](https://global.discourse-cdn.com/mcneel/uploads/default/original/4X/5/b/4/5b4a720dd0edba339b2a26f69357aba95f13a486.png)

you can use CurveClosestPoint to find the parameter of the closest point to B along A:

 ![image](https://global.discourse-cdn.com/mcneel/uploads/default/original/4X/1/7/3/173667d35311eecdbf7c4f7bb6872cb1bfdcdbbf.png)

note that the lengths of the shattered curves is different 👍

 ![image](https://global.discourse-cdn.com/mcneel/uploads/default/original/4X/b/d/b/bdb7d0682ea85ee70724d4a3365f48337cfa8046.png)

similar thing happens here:

 ![image](https://global.discourse-cdn.com/mcneel/uploads/default/original/4X/f/7/d/f7d9316b8d2f02ec857f400a7824b7d9103b79da.png)

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<div class="post-metadata">

**Author:** ![Plamen\_Panchev](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/plamen_panchev/32/347478_2.png) [@Plamen\_Panchev](https://discourse.mcneel.com/u/Plamen_Panchev)\
**Post date:** [October 24, 2022, 1:33pm UTC](https://discourse.mcneel.com/t/why-doesnt-grasshopper-shatter-at-the-specified-point/149588/3 "2022-10-24T13:33:43Z")

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Thank you very much, this was exactly what I was looking for.  
Could I just ask you why was it splitting it at a different point then, and not just translating directly the point I was connecting?

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<div class="post-metadata">

**Author:** ![inno](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/inno/32/544036_2.png) [@inno](https://discourse.mcneel.com/u/inno)\
**Post date:** [October 24, 2022, 4:57pm UTC](https://discourse.mcneel.com/t/why-doesnt-grasshopper-shatter-at-the-specified-point/149588/4 "2022-10-24T16:57:25Z")

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> [@Plamen\_Panchev](#):
>
> Could I just ask you why was it splitting it at a different point then, and not just translating directly the point I was connecting?

I think a 3D point cast as number returns the distance between the point itself and the Origin

that distance is a numberic value, so it’s accepted as _t_ paramenter (any number is accepted as _t_ parameter as long as it stays in the domain of the curve)  
the thing is, the distance between that point and the origin is probably not the _t_ parameter at which you want to split your curve 🙂

here are two wonderful readings on the topic by David Rutten (who happens to be the creator of Grasshopper 👍 )

> **[Curve Parameter Space](https://ieatbugsforbreakfast.wordpress.com/2013/09/27/curve-parameter-space/)**
>
> One of the more common misconceptions people have regarding computational geometry has to do with curve parameters. Since the mathematics of Nurbs curves are rather involved —much of it is certainl…

> **[Curve parameters, an analogy](https://ieatbugsforbreakfast.wordpress.com/2013/09/28/curve-parameters-an-analogy/)**
>
> While trying to explain curve parameters to my girlfriend (she was proofreading my previous blog post) we hit upon an apt analogy. Imagine you’re taking a car-trip from home to the nearest Ho…