# Raycast issues when used for point in object detection

**URL:** <https://discourse.threejs.org/t/raycast-issues-when-used-for-point-in-object-detection/38551>\
**Category:** Questions\
**Tags:** intersection, raycaster\
**Created:** [May 26, 2022, 3:10pm UTC](https://discourse.threejs.org/t/raycast-issues-when-used-for-point-in-object-detection/38551 "2022-05-26T15:10:43Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![gilad](https://yyz1.discourse-cdn.com/flex035/user_avatar/discourse.threejs.org/gilad/32/22611_2.png) [@gilad](https://discourse.threejs.org/u/gilad)\
**Post date:** [May 26, 2022, 3:10pm UTC](https://discourse.threejs.org/t/raycast-issues-when-used-for-point-in-object-detection/38551/1 "2022-05-26T15:10:43Z")

</div>

Hello,

I’m working on a CSG library and I am trying to use Raycast to determine if a triangle is **inside** or **outside** of the target object (mesh) by checking if the triangle’s mid point is inside or not.

For the most part raycasting works fine, but, I started running into precision issues that are conflicting:

1. Triangle mid point on the surface sometimes being detected as inside and sometimes as outside depends on which surface the point is (which side of a cube) and which direction is being used. ← This one is ok-ish, since I know if the triangle is coplanar or not, I can do additional tests by adding an epsilon to the point and retest.
2. Triangle mid point is **outside** of the object (not on surface/boundary) and is detected as **inside** when it is supposed to be **outside** (noticed when the target object is a Cylinder with radius bottom or top of 0).  
a. Example - [three.js raycast test 2 - JSFiddle - Code Playground](https://jsfiddle.net/giladdarshan/mao1prs4/)  
b. Another example, this time I rounded the point’s x,y,z down to integers ((-1.732050895690918, -1, -3) to (-2, -1, -3)) and the raycasting result is still **inside** instead of **outside** - [three.js raycast test 3 - JSFiddle - Code Playground](https://jsfiddle.net/giladdarshan/srbdxyhz/)
3. Triangle mid point is **inside** of the object (not on surface/boundary) and is detected as **outside** when it is supposed to be **inside** (noticed when the target object is a Icosahedron with radius 5 and detail 10).  
Example - [three.js raycast test 1 - JSFiddle - Code Playground](https://jsfiddle.net/giladdarshan/9r1te8pk/)
4. With #⁠2 and #⁠3 conflicting, how can I guarantee the inside/outside classification will be correct?

In the examples there is a small yellow sphere to show where the point is, it is not part of the raycast flow.

I tried searching online and in the forums for clues as to why I get the conflicting issues but no luck.  
Any help will be appreciated!

Thank you.