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<TITLE> Description of Objects in VPython</TITLE>
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<H1 CLASS="Heading-1"> <font color="#0000A0">The label Object</font></H1>
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<P CLASS="Normal"> With the label object you can display text in a box. Here
are simple examples (in the second label statement, note the standard Python
scheme for formatting numerical values, where 1.5f means 1 figure before the
decimal point and 5 after):</P>
<DIV>
<H2 CLASS="program0"> box(pos=(0,0,0), color=color.red)</H2>
<H2 CLASS="program0">label(pos=(0,0.25,0), text='This is a box')</H2>
<H2 CLASS="program0">label(pos=(0,-0.25,0), text='pi = %1.5f' % pi)</H2>
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<P CLASS="Normal"><IMG SRC="VisualRef-7.gif" ALIGN="RIGHT"> There are many additional
label options. In the accompanying diagram, a sphere representing the Earth
(whose center is at <span class="attribute"> earth.pos</span>) has an associated
label carrying the text "Earth" in a box, connected to the sphere
by a line which stops at the surface of the sphere:</P>
<DIV>
<H2 CLASS="program0">
earthlabel = label(pos=earth.pos, text='Earth', xoffset=20, yoffset=12, space=earth.radius, height=10, border=6)</H2>
<P CLASS="Normal"> A unique feature of the label object is that several attributes
are given in terms of screen pixels instead of the usual "world-space"
coordinates. For example, the height of the text is given in pixels, with
the result that the text remains readable even when the sphere object is
moved far away. Other pixel-oriented attributes include <span class="attribute">xoffset</span>,
<span class="attribute">yoffset</span>, and <span class="attribute">border</span>.
Here are the label attributes:</P>
<P CLASS="attributes"> <span class="attribute">pos</span>; <span class="attribute">x</span>,<span class="attribute">y</span>,<span class="attribute">z</span>
The point in world space being labeled</P>
<P CLASS="attributes"> <span class="attribute">xoffset</span>, <span class="attribute">yoffset</span>
The x and y components of the line, in pixels (see diagram)</P>
<P CLASS="attributes"> <span class="attribute">text</span> The text to be
displayed, such as 'Earth'<br>
(Line breaks can be included as \n, as in label.text = "Three\nlines\nof
text")</P>
<P CLASS="attributes"> <span class="attribute">height</span> Height of the font
in pixels</P>
<P CLASS="attributes"> <span class="attribute">color</span>, <span class="attribute">red</span>,
<span class="attribute">green</span>, <span class="attribute">blue</span>
Color of the text</P>
<P CLASS="attributes"> <span class="attribute">opacity</span> Opacity of the
background of the box, default 0.66<BR>
(0 transparent, 1 opaque, for objects behind the box)</P>
<P CLASS="attributes"> <span class="attribute">border</span> Distance in pixels
from the text to the surrounding box</P>
<P CLASS="attributes"> <span class="attribute">box</span> 1 if the box should
be drawn (default), else 0</P>
<P CLASS="attributes"> <span class="attribute">line</span> 1 if the line from
the box to pos should be drawn (default), else 0</P>
<P CLASS="attributes"> <span class="attribute">linecolor</span> Color of the line
and box</P>
<P CLASS="attributes"> <span class="attribute">space</span> World-space radius
of a sphere surrounding pos,<BR>
into which the connecting line does not go</P>
<P CLASS="attributes"> <span class="attribute">font</span> Optional name of
the font, such as `helvetica'</P>
<P CLASS="attributes"> </P>
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