Bounding box that is parallel to the camera - three.js

Question

My problem is how to define the camera location, given a lookAt vector, when the camera is not on the z axis, so it captures all objects according to its fov and aspect.
I think I need to get a bounding box of my objects that is perpendicular to the camera's lookAt and top and bottom front and back edges are parallel to the xz plane. Then the back of the bounding box is the 'far' plane and I can calculate the distance from it (or fov) and set the camera accordingly.
My question is, how to get such a bounding box (Box3 instance), given some objects on the scene and the lookAt vector ?

Answer 1

My question is, how to get such a bounding box (Box3 instance), given some objects on the scene and the lookAt vector ?
Instances of THREE.Box3 are axis-aligned bounding boxes. No matter how the camera is rotated, it is not possible to generate a different bounding box for a given set of 3D objects.
Maybe you can use a quite common approach 3D viewers which ensures to always display an imported 3D object in the viewport. Exemplary code from the open source glTF viewer looks like this:
const aabb = new THREE.Box3().setFromObject( object );
const center = aabb.getCenter( new THREE.Vector3() );
const size = aabb.getSize( new THREE.Vector3() ).length();
// centering object
object.position.x += ( object.position.x - center.x );
object.position.y += ( object.position.y - center.y );
object.position.z += ( object.position.z - center.z );
// update camera
camera.near = size / 100;
camera.far = size * 100;
camera.updateProjectionMatrix();
camera.position.copy( center );
camera.position.x += size / 2.0;
camera.position.y += size / 5.0;
camera.position.z += size / 2.0;
camera.lookAt( center );