from visual import *

xmax = 2.5
scene.range = xmax
initialdistance = xmax/tan(scene.fov/2.0)
box(pos=(-1.5,0,0), color=color.red)
box(pos=(1.5,0,0), color=color.blue)

# Wait while user adjusts the view.
scene.mouse.getclick()

# Determine how far we are from the center of the scene.
savedistance = mag(scene.mouse.camera-scene.center)
# Keep a copy of current scene.forward.
saveforward = vector(scene.forward)
### Mousing changes scene.forward and can change scene.up too!
saveup = vector(scene.up)

# Wait for more mousing, but on the next click, zoom out programatically:
scene.mouse.getclick()
# Changing scene.range affects the view (but not vice versa).
scene.range = 2*scene.range
savedistance *= scene.range.x/xmax

# Wait while user changes the view, then restore the saved view.
scene.mouse.getclick()
# Determine the new distance from the center.
distance = mag(scene.mouse.camera-scene.center)
# Adjust the range based on the new distance.
scene.range = (savedistance/distance)*xmax
# Reset the viewing direction.
scene.up = saveup
scene.forward = saveforward