computeBoundingSphere() {

		const geometry = this.geometry;
		const count = this.count;

		if ( this.boundingSphere === null ) {

			this.boundingSphere = new Sphere();

		}

		if ( geometry.boundingSphere === null ) {

			geometry.computeBoundingSphere();

		}

		this.boundingSphere.makeEmpty();

		for ( let i = 0; i < count; i ++ ) {

			this.getMatrixAt( i, _instanceLocalMatrix );

			_sphere$4.copy( geometry.boundingSphere ).applyMatrix4( _instanceLocalMatrix );

			this.boundingSphere.union( _sphere$4 );

		}

	}
Computes the bounding sphere of the instanced mesh, and updates {@link InstancedMesh#boundingSphere}
The engine automatically computes the bounding sphere when it is needed, e.g., for ray casting or view frustum culling.
You may need to recompute the bounding sphere if an instance is transformed via {@link InstancedMesh#setMatrixAt}.