Threejs Fit plane to screen

gistfile1.js

var cameraZ = camera.position.z;
var planeZ = 5;
var distance = cameraZ - planeZ;
var aspect = viewWidth / viewHeight;
var vFov = camera.fov * Math.PI / 180;
var planeHeightAtDistance = 2 * Math.tan(vFov / 2) * distance;
var planeWidthAtDistance = planeHeightAtDistance * aspect;

// or

let dist = camera.position.z - mesh.position.z;
let height = ... // desired height to fit
camera.fov = 2 * Math.atan(height / (2 * dist)) * (180 / Math.PI);
camera.updateProjectionMatrix();


// Basically solving an AAS triangle https://www.mathsisfun.com/algebra/trig-solving-aas-triangles.html
https://i.stack.imgur.com/PgSn3.jpg