Bounding Sphere

To compute a bounding sphere, find a center, and then the most distant vertex:

xsum,ysum,zsum = 0,0,0
for v in obj.vertices:
    xsum += v[0]
    ysum += v[1]
    zsum += v[2]
center = [ xsum / len(obj.vertices) , ysum / len(obj.vertices), zsum / len(obj.vertices) ]

radius = 0
for v in obj.vertices:
    d = distance(v, center)
    if d > radius:
        radius = d