from visual import *
##from time import clock

# If you want to access scene.range before any user adjustments
# have been made (zoom or spin), you need to wait for the scene
# to be rendered and autoscaled. In that case you need to import
# the clock() function to make it possible to wait for 0.1 s (say).
# But if you wait on a mouse click for the user to complete zoom
# or spin, you don't need to pause the 0.1 s.

box(pos=(-1.5,0,0), color=color.red)
box(pos=(1.5,0,0), color=color.blue)
##t = clock()
##while clock() < t+0.1:
##    continue

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

# Determine the outer bounds of the objects displayed.
### saverange has to be a new object too (not just a reference)
### Actually, since mousing never changes scene.range, this one wouldn't
### bite you until you change it programatically.
saverange = vector(scene.range)

# 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 to 50% programatically:
scene.mouse.getclick()
zoom = 0.5
scene.range = scene.range/zoom
### Changing scene.range *does* shift the camera (but not vice versa).
### The new relationship between camera and scene is not under our
### control, and seemes to supercede the one saved above! We have to adjust the
### saved distance or the restored view will be off.
savedistance *= mag(scene.range)/mag(saverange)

# 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)*saverange
# Reset the viewing direction.
scene.up = saveup
scene.forward = saveforward