from vpython import *
# John Coady
title = "Click and drag the mouse in the 3D canvas to insert and drag a small sphere."
scene.title = title
scene.range = 3
b = box(pos=vector(0,0,0), color=color.green)
drag = False
s = None
def grab(evt):
global s, drag
scene.title = 'Drag the sphere.'
drag = True
s = sphere(pos=evt.pos, radius=0.1, color=color.red)
def move(evt):
if drag:
s.pos = evt.pos
def drop(evt):
global drag
scene.title = title
s.color = color.cyan
drag = False
scene.bind('mousedown',grab)
scene.bind('mousemove',move)
scene.bind('mouseup',drop)