Visible width/height with threejs perspective camera

gistfile1.txt

// https://discourse.threejs.org/t/functions-to-calculate-the-visible-width-height-at-a-given-z-depth-from-a-perspective-camera/269

function visibleHeightAtDepth(depth, camera) {
    // compensate for cameras not positioned at z=0
    const cameraOffset = camera.position.z;
    if ( depth < cameraOffset ) depth -= cameraOffset;
    else depth += cameraOffset;
    // vertical fov in radians
    const vFOV = camera.fov * Math.PI / 180;
    // Math.abs to ensure the result is always positive
    return 2 * Math.tan( vFOV / 2 ) * Math.abs( depth );
}
function visibleWidthAtDepth(depth, camera) {
    const height = visibleHeightAtDepth( depth, camera );
    return height * camera.aspect;
}

export default {
    visibleHeightAtDepth,
    visibleWidthAtDepth
};