glodrei/docs/misc/use-intersect.mdx

useful add-ons for react-three-fiber

---
title: useIntersect
sourcecode: src/core/useIntersect.tsx
---

<Grid cols={4}>
  <li>
    <Codesandbox id="gsm1y" />
  </li>
</Grid>

A very cheap frustum check that gives you a reference you can observe in order to know if the object has entered the view or is outside of it. This relies on [THREE.Object3D.onBeforeRender](https://threejs.org/docs/#api/en/core/Object3D.onBeforeRender) so it only works on objects that are effectively rendered, like meshes, lines, sprites. It won't work on groups, object3d's, bones, etc.

```jsx
const ref = useIntersect((visible) => console.log('object is visible', visible))
return <mesh ref={ref} />
```