Dimension of parent scene or any 3d scene

let sphere = 
meshes
.
add
(Sphere { radius: 1. }.mesh().uv(32, 18));

I am trying to create an explosion ball for entities with scene assets but I don't know how wrap the entities perfectly inside the ball.
My idea is to get the size of the entity that is it's span in the space, and then spawn a sphere(for now) around it which perfectly fits. The sphere is generated by using bevy default shapes.