# Three-mesh-bvh coplanar intersection issue

**URL:** https://discourse.threejs.org/t/three-mesh-bvh-coplanar-intersection-issue/77487
**Category:** Questions
**Tags:** three-mesh-bvh
**Created:** [February 3, 2025, 1:29pm UTC](https://discourse.threejs.org/t/three-mesh-bvh-coplanar-intersection-issue/77487 "2025-02-03T13:29:45Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![Ayush\_Ranjan\_Sharma](https://yyz1.discourse-cdn.com/flex035/user_avatar/discourse.threejs.org/ayush_ranjan_sharma/32/51846_2.png) [@Ayush\_Ranjan\_Sharma](https://discourse.threejs.org/u/Ayush_Ranjan_Sharma)
#### Post date: [February 3, 2025, 1:29pm UTC](https://discourse.threejs.org/t/three-mesh-bvh-coplanar-intersection-issue/77487/1 "2025-02-03T13:29:45Z")

</div>

Hi,  
I’m facing issue while intersection operation. I am intersecting custom buffer geometry with box geometry, both of these geometries have same height and in resulting intersection I’m getting missing surface on one side (top/bottom).  
In example figure, A = Box Geometry, B = Buffer geometry. On taking A ∩ B, I get unclosed surface in shaded region in resulting image. (Sorry cannot provide exact images due to security reasons).

 ![Screenshot 2025-02-03 110705](https://canada1.discourse-cdn.com/flex035/uploads/threejs/original/3X/1/3/1364b2fb82f1b26d4bd91add5d9878d746eeeeb9.jpeg)

I have checked the normals of top and bottom are pointing correctly and suspect this to be issue with co-planarity of surfaces. Any way to resolve this ?