Box3.expandFromObject doesn't work when the given Line doesn't have vertices

[woo-cie]

Description of the problem

When giving object3D with an empty bounding box to expandFromObject, new Box3 is not empty.
Max of new Box3 is (+Inf, +Inf, +Inf) and min of that is (-Inf, -Inf, -Inf).

const line = new Line(new Geometry());
line.geometry.computeBoundingBox();

console.log(line.geometry.boundingBox.min);
// Vector3 {x: Infinity, y: Infinity, z: Infinity, constructor: Object}
console.log(new Box3().setFromObject(line).min);
// Vector3 {x: -Infinity, y: -Infinity, z: -Infinity, constructor: Object}

console.log(line.geometry.boundingBox.max);
// Vector3 {x: -Infinity, y: -Infinity, z: -Infinity, constructor: Object}
console.log(new Box3().setFromObject(line).max);
// Vector3 {x: Infinity, y: Infinity, z: Infinity, constructor: Object}

This is because expandFromObject use expandFromPoint to set max and min.
To fix this, it should set max and min directly or ignore when max = -Inf and min = +Inf.

three.js/src/math/Box3.js

Lines 265 to 266 in c23b245

	this.expandByPoint( _box.min );
	this.expandByPoint( _box.max );

Three.js version

r111 and later

Browser

• All of them

OS

• All of them

[Mugen87]

You are right. Creating an AABB from a 3D objects like mesh, point cloud or line with an initial geometry object should be empty. Right now, this code returns false:

console.log( new THREE.Box3().setFromObject( new THREE.Mesh() ).isEmpty() ); // false