# BooleanUnion error on simple object

**URL:** <https://discourse.mcneel.com/t/booleanunion-error-on-simple-object/199660>\
**Category:** Rhino\
**Tags:** windows\
**Created:** [February 15, 2025, 2:06pm UTC](https://discourse.mcneel.com/t/booleanunion-error-on-simple-object/199660 "2025-02-15T14:06:22Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Holo](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/holo/32/496872_2.png) [@Holo](https://discourse.mcneel.com/u/Holo)\
**Post date:** [February 15, 2025, 2:06pm UTC](https://discourse.mcneel.com/t/booleanunion-error-on-simple-object/199660/1 "2025-02-15T14:06:22Z")

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@wim  
This is a simple cylinder that has been rotated into it’s position. Nothing fancy at all.

Please try this:  
PolarArray so they become 3 units around Z axis (or on XY plane if that makes more sense)  
Try to BooleanUnion two of them.

Something goes wrong and Rhino won’t give any clues.

If you run intersection on them you’ll get this result:

 ![image](https://global.discourse-cdn.com/mcneel/uploads/default/original/4X/3/c/a/3caa9cc7143843d53daf81fb48d13695e27ceb69.png)  
Ans similar if you explode the pipes first.

So I figured it this happens on such a simple object then that would be a good case study for a lot of more complex scenarios too.

[PolarArray3xAndBoolenUnionTwo\_Fail.3dm](https://discourse.mcneel.com/uploads/short-url/iYzMjrcg3JwA23xHI1D6cbnd6lM.3dm) (37.2 KB)

EDIT: I see Rhino 8 manages to boolean union one of the three combinations, Rhino 7 manages zero of them and Rhino WIP manages two of them…

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**Author:** ![Measure](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/measure/32/651816_2.png) [@Measure](https://discourse.mcneel.com/u/Measure)\
**Post date:** [February 15, 2025, 3:48pm UTC](https://discourse.mcneel.com/t/booleanunion-error-on-simple-object/199660/2 "2025-02-15T15:48:48Z")

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I see the same thing. Also, `_BooleanDifference` says “Objects do not intersect. Nothing done.”

`_Boolean2Objects` gets it right though.

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**Author:** ![Measure](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/measure/32/651816_2.png) [@Measure](https://discourse.mcneel.com/u/Measure)\
**Post date:** [February 15, 2025, 3:53pm UTC](https://discourse.mcneel.com/t/booleanunion-error-on-simple-object/199660/3 "2025-02-15T15:53:06Z")

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I’m guessing it has to do with this intersection point being exactly on the Z axis.

 ![image](https://global.discourse-cdn.com/mcneel/uploads/default/original/4X/c/e/4/ce4bf90152fc78ea25a7aff6c10478dd796eb204.jpeg)