ThreeJS - Check if point is in front of camera (inside FOV)

threejs-point-in-front-of-camera.js

/*
  NOTES:
  basic source: https://discourse.threejs.org/t/detect-if-target-is-behind-the-camera-bis/219/2
  you could also use a frustum: https://threejs.org/docs/index.html#api/en/math/Frustum.containsPoint

  we assume the InFrontOfCamera will be called many times each frame - so we want to prepare the camera values it uses to lower processing cost
*/

const CAM_FOV = 60;
const CAM_FOV2 = (Math.PI / 360) * (360 - CAM_FOV);


function inFrontOfCamera(cameraPosition, cameraDirection, position) {
  let p = new THREE.Vector3();
  p.copy(position);
  return (p.sub(cameraPosition).angleTo(cameraDirection)) < (Math.PI / CAM_FOV2);
}

const aspect = 1920 / 1080;
const near = 1;
const far = 25000.0;
const camera = new THREE.PerspectiveCamera(CAM_FOV, aspect, near, far);
cameraDirection = new THREE.Vector3();

// each frame
camera.getWorldDirection(cameraDirection);

let testPoint = new THREE.Vector3(1, 1, 1);
if (inFrontOfCamera(camera.position, cameraDirection, testPoint)) {
  // do stuff
}