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<H1 CLASS="Heading-1"> <font color="#0000A0">The cylinder Object</font></H1>
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<P CLASS="Normal"> <IMG SRC="VisualRef-1.gif" ALIGN="RIGHT"> Here is an example
of how to make a cylinder, naming it "rod" for future reference:</P>
<DIV>
<H2 CLASS="program0"> rod = cylinder(pos=(0,2,1), axis=(5,0,0), radius=1)</H2>
<P CLASS="Normal"> The center of one end of this cylinder is at x=0, y=2,
and z=1. Its axis lies along the x axis, with length 5, so that the other
end of the cylinder is at (5,2,1), as shown in the accompanying diagram.</P>
<P CLASS="Normal"> You can modify the position of the cylinder after it has
been created, which has the effect of moving it immediately to the new position:</P>
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<DIV>
<P CLASS="program"> rod.pos = (15,11,9) # change position (x,y,z)</P>
<P CLASS="program"> rod.x = 15 # only change pos.x</P>
<P CLASS="Normal"> If you create an object such as a cylinder but without
giving it a name such as <span class="attribute">rod</span>, you can't refer
to it later. This doesn't matter if you never intend to modify the object.</P>
<P CLASS="Normal"> Since we didn't specify a color, the cylinder will be the
current "foreground" color (see <a href="display.html">Controlling
One or More Visual Display Windows</a>). The default foreground color is
white. After creating the cylinder, you can change its color:</P>
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<P CLASS="program"> rod.color = (0,0,1) # make rod be blue</P>
<P CLASS="Normal"> This will make the cylinder suddenly turn blue, using the
so-called RGB system for specifying colors in terms of fractions of red,
green, and blue. (For details on choosing colors, see <a href="color.html">Specifying
Colors</a>.) You can set individual amounts of red, green, and blue like
this:</P>
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<P CLASS="program"> rod.red = 0.4</P>
<P CLASS="program"> rod.green = 0.7</P>
<P CLASS="program"> rod.blue = 0.8</P>
<P CLASS="Normal"> The cylinder object can be created with other, optional
attributes, which can be listed in any order. Here is a full list of attributes,
most of which also apply to other objects:</P>
<P CLASS="attributes"> <font color="#FF0000" class="attribute">pos</font>
Position: the center of one end of the cylinder; default = (0,0,0)<BR>
A triple, in parentheses, such as (3,2,5)</P>
<P CLASS="attributes"> <font color="#FF0000">axis</font> The axis points from
pos to the other end of the cylinder, default = (1,0,0)</P>
<P CLASS="attributes"> <span class="attribute">x</span>, <span class="attribute">y</span>,
<span class="attribute">z</span> Essentially the same as pos.x, pos.y, pos.z,
defaults are all 0</P>
<P CLASS="attributes"> <span class="attribute">radius</span> The radius of
the cylinder, default = 1</P>
<P CLASS="attributes"> <span class="attribute">length</span> Length of axis;
if not specified, axis determines the length, default = 1<BR>
If length is specified, it overrides the length given by axis</P>
<P CLASS="attributes"> <span class="attribute">color</span> Color of object,
as a red-green-blue (RGB) triple: (1,0,0) is pure red, default = (1,1,1),
which is color.white</P>
<P CLASS="attributes"> <span class="attribute">red</span>, <span class="attribute">green</span>,
<span class="attribute">blue</span> (can set these color attributes individually),
defaults are all 1</P>
<P CLASS="attributes"> <span class="attribute">up</span> Which side of the
cylinder is "up"; this has only a subtle effect on the 3D appearance
of the cylinder, default (0,1,0)</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 a box, sphere, or ring it corresponds to the center of the object.
</P>
<P CLASS="Normal"> When you start a VPython program, for convenience Visual
creates a display window and names it <span class="attribute">scene</span>.
By default, objects that you create go into that display window. See <a href="display.html">Controlling
One or More Visual Display Windows</a> later in this reference for how you
can create additional display windows and place objects in them.</P>
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