The following attributes apply to all VPython objects:
visible If false (0),
object is not displayed; e.g. ball.visible = 0
Use ball.visible = 1 to make the ball
visible again.
frame Place this object into a specified frame, as in ball = sphere(frame = f1)
display When you start a VPython program, for convenience Visual creates a display window and names it scene. By default, objects you create go into that display window. You can choose to put an object in a different display like this:
scene2 = display( title = "Act IV, Scene 2" )rod = cylinder( display = scene2 )The function display.get_selected() returns a reference to the display in which objects are currently being created.
__class__ Name of the class of object. For example, ball.__class__ is sphere is true if ball is a sphere object. There are two underscores before and after the word class. In a list of visible objects provided by scene.objects, if obj is in this list you can determine the class of the object with obj.__class__.
__copy()__ Makes a copy of an object. There are two underscores before and after the copy(). Without any arguments, this results in creating a second object in the exact same position as the first, which is probably not what you want. The __copy__() function takes a list of keyword=value argument pairs which are applied to the new object before making it visible. For example, to clone an object from one display to another, you would execute: new_object = old_object.__copy__( display=new_display). Restriction: If the original object is within a frame, and the new object is on a different display, you must supply both a new display and a new frame for the new object (the new frame may be None). This is due to the restriction that an object may not be located within a frame that is in a separate display. The attribute __members__ used to give a list of all the object's attributes but is no longer available in VPython. Its main use was in copying objects.
Here is an example that uses the __copy()__ function. The following routine copies all of the Visual objects currently existing in one display into a previously defined second display:
def clone_universe( new_display, old_display):
# Create a dictionary of frames in the old display
# to the corresponding frames in the new display.
frames = dict()
# Initialize the lookup dictionary
for obj in old_display.objects:
if obj.__class__ == frame:
frames[obj] = obj.__copy__( frame=None, display=new_display)
# For each old reference frame that was within another reference frame,
# place the new reference frame within the appropriate frame in the new
# display. Here old is an object and new is its frame in the new display.
for old, new in frames.iteritems():
if old.frame:
new.frame = frames[old.frame]
# Copy over the universe.
for obj in old_display.objects:
if obj.__class__ == frame:
# Already taken care of above.
continue
if obj.frame:
# Then initialize with the corresponding reference frame in the new
# display.
obj.__copy__( display=new_display, frame=frames[obj.frame])
else:
# Don't need to care about the frame attribute, since it is None.
obj.__copy__( display=new_display)
See Controlling One or More Visual Display Windows for more information on creating and manipulating display objects.
