Visible Portion of some element at certain distance, plane.

Threejs-ElementSizeOnFov.js

import {MathUtils} from "three";

// this gives the "visible" plane sizes that is visible from the camera at a certain distance
export default function(distance, camera) {
  const vFOV = MathUtils.degToRad(camera.fov);
  const height = 2 * Math.tan(vFOV / 2) * distance;
  const width = height * camera.aspect;
  return { width, height };
}