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<td width="10" height="272" valign="top" bgcolor="#DDDDDD"><p> </p> </td>
<td width="173" valign="top" bgcolor="#DDDDDD"><p class="Normal"><a href="index.html">Home</a></p>
<p class="Normal">If you're new to Python <br />
and VPython: <a href="VisualIntro.html">Introduction</a></p>
<p class="Normal">A VPython <a href="VPython_Intro.pdf" target="_blank">tutorial</a></p>
<p class="Normal"><a href="primitives.html">Pictures</a> of 3D objects</p>
<p class="Normal">Choose a 3D object:</p>
<select name="jumpMenu4" id="jumpMenu4" onchange="MM_jumpMenu('parent',this,0)">
<option>Choose an object</option>
<option value="cylinder.html">Overview</option>
<option value="arrow.html">arrow</option>
<option value="box.html">box</option>
<option value="cone.html">cone</option>
<option value="convex.html">convex</option>
<option value="curve.html">curve</option>
<option value="cylinder.html">cylinder</option>
<option value="ellipsoid.html">ellipsoid</option>
<option value="faces.html">faces</option>
<option value="frame.html">frame</option>
<option value="helix.html">helix</option>
<option value="label.html">label</option>
<option value="lights.html">lights</option>
<option value="points.html">points</option>
<option value="pyramid.html">pyramid</option>
<option value="ring.html">ring</option>
<option value="sphere.html">sphere</option>
</select>
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<option>Choose an option</option>
<option value="color.html">Color & Opacity</option>
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<option value="materials.html">Materials & Textures</option>
<option value="defaults.html">Defaults</option>
<option value="rate.html">Animation Speed</option>
<option value="rotation.html">Rotations</option>
<option value="options.html">Additional Options</option>
<option value="delete.html">Delete an Object</option>
<option value="float.html">3/4 = 0?</option>
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<p class="Normal"><a href="vector.html">Vector operations </a></p>
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<p class="Normal"><a href="factorial.html">factorial/combin</a></p>
<p class="Normal">What's new in <a href="new_features.html">Visual 5</a></p>
<p class="Normal"><a href="http://vpython.org" target="_blank">VPython web site</a><br />
<a href="license.txt" target="_blank">Visual license</a><br />
<a href="http://www.python.org" target="_blank">Python web site</a> <br />
<a href="http://www.python.org/doc/2.5.2/lib/module-math.html" target="_blank">Math module</a> (sqrt etc.)<br />
<a href="http://www.scipy.org/Documentation" target="_blank">Numpy module</a> (arrays) </p></td>
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<div>
<h1 class="Heading-1"> <font color="#0000A0">Additional Attributes</font></h1>
</div>
<div>
<p class="Normal"> The following attributes apply to all VPython objects:</p>
<p class="attributes"> <span class="attribute">visible</span> If False,
object is not displayed; e.g. <span class="attribute">ball.visible = False</span><em class="program"><br />
</em> Use <span class="attribute">ball.visible = True</span> to make the ball
visible again.</p>
<p class="attributes"><span class="attribute">frame</span> Place this object
into a specified frame, as in <span class="attribute">ball = sphere(frame
= f1)</span> </p>
<p class="attributes"> <span class="attribute">display</span> When you start
a VPython program, for convenience Visual creates a display window and names
it <span class="attribute">scene</span>. By default, objects you create go
into that display window. You can choose to put an object in a different display
like this: </p>
<p class="program">scene2 = display( title = "Act IV, Scene 2" ) <br />
rod = cylinder( display = scene2 )</p>
<p class="Normal">Executing <span class="attribute">myscene = </span><font color="#FF0000">display.get_selected()</font> returns
a reference to the display in which objects are currently being
created. Given a specific display named scene2, <span class="attribute">scene2.select()</span><span class="attributes"> makes
scene2 be the "selected display", so that objects
will be drawn into scene2 by default. </span></p>
<p class="Normal">There is a <a href="rotation.html">rotate function</a> for
all objects other than curve, convex, faces, and points (which can
be put into a frame and the frame rotated).</p>
<p class="attributes"><span class="attribute">__class__</span> Name of the class
of object. For example, <span class="attribute">ball.__class__ is sphere</span> is true if <span class="attribute">ball</span> is a sphere object. There are
two underscores before and after the word <span class="attribute">class</span>.
In a list of visible objects provided by <a href="display.html">scene.objects</a>,
if <span class="attribute">obj</span> is in this list you can determine the
class of the object with <span class="attribute">obj.__class__</span>. <span class="Normal">You can check for a specific kind of object by using a standard Python function: isinstance(obj, sphere) is true if "obj" is a sphere object.</span></p>
<p class="attributes"><span class="attribute">__copy__</span><span class="attribute">()</span> Makes
a copy of an object. There are two underscores before and after <span class="attribute">copy</span>.
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 <font color="#FF0000">__copy__()</font> 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: <font color="#FF0000">new_object
= old_object.__copy__( display=new_display)</font>. 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.</p>
<p class="Normal">Here is an example that uses the <span class="attribute">__copy__()</span> function.
The following routine copies all of the Visual objects currently existing
in one display into a previously defined second display, as long as
there are no nested frames (frames within frames):</p>
<p class="program">def clone_universe( new_display, old_display):<br />
# Create a dictionary of frames in old display to <br />
# the corresponding frames in the new display.<br />
frames = {} # create empty dictionary <br />
for obj in old_display.objects:<br />
if obj.__class__ == frame:<br />
frames[obj] = obj.__copy__( frame=None, <br />
display=new_display)<br />
# For each old frame within another reference frame,<br />
# place the new frame in appropriate frame in new<br />
# display. Here old is an object and new is its<br />
# frame in the new display.<br />
for old, new in frames.iteritems():<br />
if old.frame:<br />
new.frame = frames[old.frame]<br />
# Copy over the universe.<br />
for obj in old_display.objects:<br />
if obj.__class__ == frame:<br />
# Already taken care of above.<br />
pass<br />
elif obj.frame:<br />
#
Initialize with the corresponding frame<br />
# in the new display:<br />
obj.__copy__( display=new_display, <br />
frame=frames[obj.frame])<br />
else:<br />
#
No frame issue;<br />
obj.__copy__( display=new_display)</p>
<p class="Normal">See <a href="display.html">Controlling One or More Visual
Display Windows</a> for more information on creating and manipulating display
objects.</p>
<p class="Normal"> </p>
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