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<TITLE> Description of Objects in VPython</TITLE>
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<H1 CLASS="Heading-1"> <font color="#0000A0">The ellipsoid Object</font></H1>
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<P CLASS="Normal"> A long ellipsoid object looks like a cigar; a short one looks
like somewhat like a pill. Its cross sections are circles or ellipses. The
elllipsoid object has the same attributes as the <a href="box.html">box object</a>
and it can be thought of as fitting inside a box of the same dimensions:</P>
<DIV>
<H2 CLASS="program0"> myell = ellipsoid(pos=(x0,y0,z0), length=L, height=H,
width=W) </H2>
<P CLASS="Normal"> The given position is in the center of the ellipsoid, at
(x0, y0, z0). This is different from cylinder, whose pos attribute is at
one end of the cylinder. Just as with a cylinder, we can refer to the individual
vector components of the ellipsoid as<span class="attribute"> myell.x</span>,
<span class="attribute">myell.y</span>, and <span class="attribute">myell.z</span>.
The length from end to end (along the x axis) is L , the height (along the
y axis) is H , and the width is W (along the z axis). For this ellipsoid,
we have <span class="attribute">myell.axis = (L, 0, 0)</span> . Note that
the axis of an ellipsoid is just like the axis of a cylinder. </P>
<P CLASS="Normal"> For an ellipsoid that isn't aligned with the coordinate
axes, additional issues come into play. The orientation of the length of
the ellipsoid is given by the axis (see diagrams shown with the documentation
on the <a href="box.html">box object</a>):</P>
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<DIV>
<H2 CLASS="program0"> myell = ellipsoid(pos=(x0,y0,z0), axis=(a,b,c), length=L,<BR>
height=H, width=W) </H2>
<P CLASS="Normal"> The axis attribute gives a direction for the length of
the ellipsoid, and the length, height, and width of the ellipsoid are given
as before (if a length attribute is not given, the length is set to the
magnitude of the axis vector). </P>
<P CLASS="Normal"> The ellipsoid object has the following attributes and default
values, like those for cylinders: <span class="attribute">pos<font color="#000000">
(0,0,0)</font></span>, <span class="attribute">x</span><span class="attribute"><font color="#000000">
(0)</font></span>, <span class="attribute">y<font color="#000000">(0)</font></span>,
<span class="attribute">z<font color="#000000">(0)</font></span>, <span class="attribute">axis<font color="#000000">
(1,0,0)</font></span>, <span class="attribute">length<font color="#000000">
(1)</font></span>, <span class="attribute">color<font color="#000000"> (1,1,1)
which is color.white</font></span>, <span class="attribute">red<font color="#000000">
(1)</font></span>, <span class="attribute">green<font color="#000000"> (1)</font></span>,
<span class="attribute">blue<font color="#000000"> (1)</font></span>, and
<span class="attribute">up<font color="#000000"> (0,1,0)</font></span>.
Additional box attributes:</P>
</DIV>
<DIV>
<P CLASS="attributes"> <span class="attribute">height</span> In the y direction
in the simple case, default is 1</P>
<P CLASS="attributes"> <span class="attribute">width</span> In the z direction
in the simple case, default is 1</P>
<P CLASS="attributes"> <span class="attribute">size</span> (length, height,
width), default is (1,1,1)<BR>
<span class="attribute"> myell.size=(20,10,12) </span>sets length=20, height=10,
width=12</P>
<P CLASS="Normal"> Note that the <span class="attribute">pos</span> attribute
for cylinder, arrow, cone, and pyramid corresponds to one end of the object,
whereas for an ellipsoid, box, sphere, or ring it corresponds to the center
of the object. </P>
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<H1 CLASS="Heading-1"><br>
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