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<article xmlns="http://docbook.org/ns/docbook" version="5.0">
  <info><title>Learning Viewing Options in <application>MGED</application></title>
    

    <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../books/en/tutorial_series_authors.xml" xpointer="Intro_MGED_Tutorial_Series_II_authors"/>

    <legalnotice>
       <para>Approved for public release; distribution is unlimited</para>
   </legalnotice>
  </info>

    <para xml:id="learning_viewing_options_overviewlist">
     In this lesson, you will:
      
      <itemizedlist mark="bullet">
	<listitem>
	  <para>Create a model radio.</para>
	</listitem> 
	<listitem>
	  <para>Locate  viewing information in the Command Window.</para>
	</listitem> 
	<listitem>
	  <para>Identify elements of the <application>MGED</application> viewing system.</para>
	</listitem> 
	<listitem>
	  <para>View your radio from different angles.</para>
	</listitem> 
	<listitem>
	  <para>Work with Shift Grips.</para>
	</listitem> 
      </itemizedlist>
    </para>

    <para xml:id="learning_viewing_options_intropara1">
      Models in <application>BRL-CAD</application> are constructed in a single xyz coordinate system, which
      we sometimes refer to as model space. The Graphics Window of <application>MGED</application> displays
      a portion of this space. The xyz coordinate system is used for specifying
      both the geometry and the view of the geometry that is presented in the
      Graphics Window.
    </para>
    
    <para xml:id="learning_viewing_options_intropara2">
      <application>MGED</application> offers a default view and a variety of optional views. You can switch
      back and forth between these views during and after model creation. This
      lesson is designed to help you understand the viewing process and options.
    </para>
    
    <section xml:id="creating_radio"><info><title>Creating a Radio</title></info>
      
     
      <para>
	To gain practice viewing actual geometry, let's build a simple geometric
	object-a "walkie-talkie" radio. Note that the commands we use to do this
	are not discussed here because our current concern is on applying the
	principles of viewing. Later lessons on creating geometry address these
	commands in detail. Begin by launching <application>MGED</application> and creating a new database
	named radio.g. Remember that one way to do this is to type the following
	command in a Terminal Window:
	
	<command>$ mged radio.g</command>
      </para>
      
      <para>
	Type the following in the Command Window, carefully checking each line
	before pressing ENTER. If you make a mistake, use BACKSPACE or the left/
	right arrow keys to make corrections before pressing ENTER (see Appendix B
	for the editing command list).
      </para>
      
      <note>
	<para>
       Be especially careful to note the difference between the numeral one  
       [1] and the letter l [l] in ell1 on the third line.
	</para>
      </note>
      
      <literallayout class="normal">
       <command>in body.s rpp 0 16 0 32 0 48[ENTER]</command>
       
       <command>in btn.s rec 8 30 36 0 3 0 4 0 0 0 0 2[ENTER]</command>
       
       <command>in btn2.s ell1 8 33 36 4 0 0 2[ENTER]</command>
       
       <command>in spkr.s tor 16 16 16 1 0 0 12 1[ENTER]</command>
       
       <command>in ant.s rcc 2 2 46 0 0 48 1[ENTER]</command>
       
       <command>in knob.s rcc 4 4 40 8 0 0 5[ENTER]</command>
      </literallayout>
      
      
      <note>
	<para>
	  Note that in the preceding Command Line expressions, btn is an        
	  abbreviation for button, ant is an abbreviation for antenna, and spkr 
	  is an abbreviation for speaker. Also note that the numbers could have 
	  been separated by single spaces. The extra spaces were inserted       
	  simply to improve readability. For some usages (e.g., the r and comb  
	  commands, which are discussed later), the number of spaces has to be  
	  exact.                   
	</para>
      </note>

      <para>
	An image similar to the following should now appear in the Graphics
	Window.

      <informalfigure>
	<mediaobject>
	  <imageobject>
	    <imagedata align="center" fileref="../../lessons/en/images/mged02_defaultradio.png" format="PNG"/>
	  </imageobject>
	  <caption>
	    <para>
	     Default View of a Radio 
	    </para>
	  </caption>
	</mediaobject>
      </informalfigure>

      </para>
    </section>
    
    <section xml:id="locating_viewing_info_cmd_window"><info><title>Locating Viewing Information in the Command Window</title></info>
      
      <para>
	Now take a minute to look at the Command Window. Even if nothing is in the
	window, enclosed in the bottom border is a string of information about the
	Graphics Window. An example string might read:
	
	<literal>cent=(8.000 16.000 24.000) sz=96.000 mm az=35.00 el=25.00 tw=-0.00
	ang=(0.00 0.00 0.00)</literal>
      </para>
      <para>
	As detailed in the following table, this information contains four groups
	of viewing data about the Graphics Window.
	
	<table frame="all"><title>Viewing Data at the Bottom of the Command Window</title>
	<tgroup cols="5" align="center" colsep="1" rowsep="1">
	  <colspec colname="c1"/>
	  <colspec colname="c2"/>
	  <colspec colname="c3"/>
	  <colspec colname="c4"/>
	  <colspec colname="c5"/>
	  <thead>
	    <row>
	      <entry>Screen Designation</entry>
	      <entry>Viewing Information</entry>
	      <entry>Location of Variables</entry>
	      <entry>Default Units</entry>
	      <entry>Default Values</entry>
	    </row>
	  </thead>
	  <tbody>
	    <row>
	      <entry>cent=</entry>
	      <entry>Center of View</entry>
	      <entry>First 3 numbers</entry>
	      <entry>Millimeters</entry>
	      <entry>0.000 0.000 0.000</entry>
	    </row>
	    <row>
	      <entry>sz=</entry>
	      <entry>Size of View</entry>
	      <entry>4th number</entry>
	      <entry>Millimeters</entry>
	      <entry>Dependent upon size selected</entry>
	    </row>
	    <row>
	      <entry>az=</entry>
	      <entry morerows="1" valign="middle">Viewing Angle</entry>
	      <entry morerows="1" valign="middle">5th and 6th numbers</entry>
	      <entry morerows="1" valign="middle">Degrees</entry>
	      <entry>35.00</entry>
	    </row>
	    <row>
	      <entry>el=</entry>
	      <entry>25.00</entry>
	    </row>
	    <row>
	      <entry>tw=</entry>
	      <entry>Twist</entry>
	      <entry morerows="1" valign="middle">7th-10th numbers</entry>
	      <entry morerows="1" valign="middle">Degrees</entry>
	      <entry>0.00</entry>
	    </row>
	    <row>
	      <entry>ang=</entry>
	      <entry>Angle of View</entry>
	      <entry>0.00 0.00 0.00</entry>
	    </row>
	  </tbody>
	</tgroup>
	</table>
      </para>
    </section>
     
    <section xml:id="viewing_system_elements"><info><title>Identifying Elements of the <application>MGED</application> Viewing System</title></info>
      
     
      <section><info><title>Center of View</title></info>
	
	<para>
	  The first set of information tells you the center of what you are viewing.
	  You can change the center of where you are looking through both the GUI
	  and the Command Window.
	</para>
	<para>
	  To change the center of your view of the radio using the GUI, press the
	  SHIFT key and any mouse button while dragging the mouse. (This is an
	  example of a Shift Grip, which is described later in this chapter.) You
	  can also change the center of view by placing the mouse pointer where you
	  want the center to be and clicking the middle mouse button.
	</para>
	<para>
	  To change the center of view using the Command Window, simply type at the
	  prompt the word center followed by three values for x, y, and z  (which is
	  the 3-D coordinate system mentioned previously). For example:
	  
	  <command>center 0 15 325.735[Enter]</command>
	  
	  As you change your view of the geometry, notice that the numbers in the
	  brackets after the cent= title will change to reflect the new center of
	  the view.
	</para>
      </section>
      
      <section><info><title>Size of View</title></info>
	
     
	<para>
	  The size of the view is the amount of model space that is shown in the
	  Graphics Window. For example, consider using a camera with a zoom lens to
	  photograph a rose. As shown in the following figures, if you zoom in on
	  the rose, it will appear large in relation to your viewing field. If you
	  zoom out, it will appear smaller. In actuality, the view size for the rose
	  image on the left might represent only 15 mm across while the view size
	  for the image on the right might represent 100 mm across. In both cases,
	  however, the actual size of the rose is the same.
	</para>
	
	<informaltable frame="none" pgwide="1">
	  <tgroup cols="2" align="center">
	    <tbody>
	      <row>
		<entry><inlinemediaobject><imageobject><imagedata fileref="../../lessons/en/images/mged02_flower_zoomin.png" scale="60"/></imageobject></inlinemediaobject></entry>
		<entry><inlinemediaobject><imageobject><imagedata fileref="../../lessons/en/images/mged02_flower_zoomout.png"/></imageobject></inlinemediaobject></entry>
	      </row>
	      <row>
		<entry>Zoom In to View Details (small size of view)</entry>
		<entry>Zoom Out to View Object 
		in Relation to Environment (large size of view)</entry>
	      </row>
	    </tbody>
	  </tgroup>
	</informaltable>
	
	<para>
	  To change the view size of your radio through the GUI, click the right
	  mouse button to zoom in and the left mouse button to zoom out. Each time
	  you click the left or right mouse button, the view of the design will
	  increase or decrease in size by a factor of 2 (i.e., two times larger or
	  two times smaller than the previous size).
	</para>
	<para>
	  You can also zoom in or out on your design by going to the View menu and
	  selecting Zoom In or Zoom Out. A drawback to this method is that you can
	  only zoom in or out one time because the drop-down menu closes once you
	  make a selection.
	</para>
	<para>
	  If you get lost at any point while creating a model, you can use the zap
	  (Z) command to clear the geometry from the Graphics Window and then recall
	  the shape with the draw command. When drawing in an empty Graphics Window,
	  <application>MGED</application> automatically sizes the view to fit what you draw into the window.
	</para>
	<para>
	  You can control the view size of your radio more accurately with the
	  Command Window. To set the size to 100 (of whichever units you have
	  selected), type at the prompt:
	  
	  <command>size 100[Enter]</command>
	</para>
	<para>
	  You can also zoom in or out on a design by typing zoom on the Command
	  Line. To make your radio appear 50% smaller, you would type:
	  
	  <command>zoom 0.5[Enter]</command>
	</para>
	<para>
	  To make your radio appear twice as large, you would type:
	  
	  <command>zoom 2[Enter]</command>
	</para>
	
	<note>
	  <para>
	    Remember that changing the view size does NOT affect the size of the
	    object. You will change the size of an object in Lesson 6.
	  </para>
	</note>
      </section>
      
      <section><info><title>Angle of View</title></info>
	
	
	<para>
	  Azimuth, elevation, and twist (all measured in degrees) determine where
	  you are in relation to the object you are viewing. Azimuth determines
	  where you are around the sides of it (i.e., to the front, left, right,
	  behind, or somewhere in between), elevation determines where you are above
	  or below it, and twist determines the angle you are rotated about the
	  viewing direction.
	</para>
	<para>
	  To better understand azimuth, imagine walking around a truck with a camera
	  to photograph it. As shown in the following illustrations, you would be at
	  0'0 azimuth if you stood directly in front of the truck to take its
	  picture. If you circled around slightly to your right, you would be at
	  35'0 azimuth. If you moved further around until you were looking directly
	  at the driver's side (in U.S. trucks), you would be at 90'0 azimuth.
	  Standing behind it would put you at 180'0 azimuth. If you were facing the
	  passenger's side, you would be at 270'0 azimuth.
	</para>
	
	<note>
	  <para>
	    The terms azimuth, elevation, and twist are similar to the terms yaw,
	    pitch, and roll, respectively, which are common terms in the
	    aerospace industry.
	  </para>
	</note>
	
	
	<informaltable frame="none" pgwide="1">
	  <tgroup cols="2" align="center">
	    <colspec colwidth="1*"/>
	    <colspec colwidth="3*"/>
  	    <tbody>
	      <row>
		<entry><inlinemediaobject><imageobject><imagedata fileref="../../lessons/en/images/mged02_truck_front.png"/></imageobject></inlinemediaobject></entry>
		<entry><inlinemediaobject><imageobject><imagedata fileref="../../lessons/en/images/mged02_truck_35_0.png"/></imageobject></inlinemediaobject></entry>
	      </row>
	      <row>
		<entry>Front (az=0, el=0)</entry>
		<entry>az=35, el=0</entry>
	      </row>
	    </tbody>
	  </tgroup>
	</informaltable>
	
	<informaltable frame="none" pgwide="1">
	  <tgroup cols="2" align="center">
	    <colspec colwidth="3*"/>
	    <colspec colwidth="1*"/>
	    <tbody>
	      <row>
		<entry><inlinemediaobject><imageobject><imagedata fileref="../../lessons/en/images/mged02_truck_left.png"/></imageobject></inlinemediaobject></entry>
		<entry><inlinemediaobject><imageobject><imagedata fileref="../../lessons/en/images/mged02_truck_rear.png"/></imageobject></inlinemediaobject></entry>
	      </row>
	      <row>
		<entry>Left (az=90, el=0)</entry>
		<entry>Rear (az=180, el=0)</entry>
	      </row>
	    </tbody>
	  </tgroup>
	</informaltable>
	
	<informaltable frame="none" pgwide="1">
	  <tgroup cols="1" align="center">
	    <tbody>
	      <row>
		<entry><inlinemediaobject><imageobject><imagedata fileref="../../lessons/en/images/mged02_truck_right.png"/></imageobject></inlinemediaobject></entry>
	      </row>
	      <row>
		<entry>Right (az=270, el=0)</entry>
	      </row>
	    </tbody>
	  </tgroup>
	</informaltable>
	
	<para>
	  Elevation, on the other hand, involves the viewer's position above or
	  below an object. In the preceding example, you circled around a truck
	  without changing your relative height. You had an elevation of 0'0, which
	  means you were level with it. As the following figures illustrate,
	  however, imagine stopping at the 35'0 azimuth position and then climbing a
	  ladder to photograph the truck from 25'0 elevation. Climbing higher, you
	  would be at 60'0 elevation. If you were directly above it with the camera
	  facing down, you would be at 90'0 elevation. If you crawled under the
	  truck and looked directly up at it, you would be at -90'0 elevation.
	</para>
	
	<informaltable frame="none" pgwide="1">
	  <tgroup cols="2" align="center">
	    <tbody>
	      <row>
		<entry><inlinemediaobject><imageobject><imagedata fileref="../../lessons/en/images/mged02_truck_35_0.png"/></imageobject></inlinemediaobject></entry>
		<entry><inlinemediaobject><imageobject><imagedata fileref="../../lessons/en/images/mged02_truck_35_25.png"/></imageobject></inlinemediaobject></entry>
	      </row>
	      <row>
		<entry>az=35, el=0</entry>
		<entry>az=35, el=25</entry>
	      </row>
	      <row>
		<entry><inlinemediaobject><imageobject><imagedata fileref="../../lessons/en/images/mged02_truck_35_60.png"/></imageobject></inlinemediaobject></entry>
		<entry><inlinemediaobject><imageobject><imagedata fileref="../../lessons/en/images/mged02_truck_35_90.png"/></imageobject></inlinemediaobject></entry>
	      </row>
	      <row>
		<entry>az=35, el=60</entry>
		<entry>az=35, el=90</entry>
	      </row>
	      <row>
		<entry><inlinemediaobject><imageobject><imagedata fileref="../../lessons/en/images/mged02_truck_270_90.png"/></imageobject></inlinemediaobject></entry>
		<entry><inlinemediaobject><imageobject><imagedata fileref="../../lessons/en/images/mged02_truck_270_-90.png"/></imageobject></inlinemediaobject></entry>
	      </row>
	      <row>
		<entry>Top (az=270, el=90)</entry>
		<entry>Bottom (az=270, el=-90)</entry>
	      </row>
	    </tbody>
	  </tgroup>
	</informaltable>
	
	<para>
	  Finally, twist (which is an optional setting in <application>MGED</application>) specifies a rotation
	  about the viewing direction. This rotation is applied to the view after
	  azimuth and elevation have been designated. So, returning to our truck
	  example, imagine standing in front of the vehicle (az=0, el=0) and then
	  tilting your camera counterclockwise 14'0. This would give your view a
	  14'0 twist angle, as shown in the following figure (on the left). Note
	  again that it is not the truck that is tipped up, but simply your view of
	  it. For more information on specifying twist, see the <command>ae</command> command in
	  Appendix A.
	  
	  <informaltable frame="none" pgwide="1">
	    <tgroup cols="1" align="center">
	      <tbody>
		<row>
		  <entry><inlinemediaobject><imageobject><imagedata fileref="../../lessons/en/images/mged02_truck_0_0_14.png"/></imageobject></inlinemediaobject></entry>
		</row>
		<row>
		  <entry>Front (az=0, el=0, tw=14)</entry>
		</row>
	      </tbody>
	    </tgroup>
	  </informaltable>
	</para>
      </section>
    </section>
    
    <section xml:id="coord_sys_summary"><info><title>Summing up on Azimuth and Elevation and the xyz Coordinate System</title></info>
      
     
      <para>
	As mentioned at the start of this lesson, <application>MGED</application> operates in a
	three-dimensional coordinate system (determined by the x, y, and z axes).
	Azimuth is measured in the xy plane with the positive x direction
	corresponding to an azimuth of 0'0. Positive azimuth angles are measured
	from the positive x axis toward and past the positive y axis. Negative
	azimuth angles are measured in the other direction.
      </para>
      
      <informalfigure>
	<mediaobject>
	  <imageobject>
	    <imagedata align="center" fileref="../../lessons/en/images/mged02_coordsys.png" scale="60" format="PNG"/>
	  </imageobject>
	  <caption>
	    <para>
	      Azimuth, Elevation, and the xyz Coordinate System
	    </para>
	  </caption>
	</mediaobject>
      </informalfigure>
      
      <para>
	If the azimuth angle is 0, then elevation is measured in the xz plane with
	+90'0 corresponding to the positive z direction and -90'0 corresponding to
	the negative z direction. However, if azimuth is not 0, these angles are
	in a plane aligned with the azimuth direction.
      </para>
    </section>
    
    <section xml:id="view_radio_angles"><info><title>Viewing Your Radio from Different Angles</title></info>
      
      
      <para>
	Let's now experiment with different views of your radio. <application>MGED</application> has several
	standard default views, which you've already seen in the preceding truck
	example. They include Top (az270, el90); Bottom (az270, el-90); Right
	(az270, el0); Left (az90, el0); Front (az0, el0); Rear (az180, el0); az35,
	el25; and az45, el45.
      </para>
      
      <para>
	Go to the View menu and try viewing your radio from different angles.
      </para>
      
      <informaltable frame="none" pgwide="1">
	<tgroup cols="2" align="center">
	  <tbody>
	    <row>
	      <entry><inlinemediaobject><imageobject><imagedata fileref="../../lessons/en/images/mged02_radio_top.png" scale="90"/></imageobject></inlinemediaobject></entry>
	      <entry><inlinemediaobject><imageobject><imagedata fileref="../../lessons/en/images/mged02_radio_35_25.png" scale="90"/></imageobject></inlinemediaobject></entry>
	    </row>
	    <row>
	      <entry>Top</entry>
	      <entry>az35,el25</entry>
	    </row>
	    <row>
	      <entry><inlinemediaobject><imageobject><imagedata fileref="../../lessons/en/images/mged02_radio_right.png" scale="90"/></imageobject></inlinemediaobject></entry>
	      <entry><inlinemediaobject><imageobject><imagedata fileref="../../lessons/en/images/mged02_radio_front.png" scale="90"/></imageobject></inlinemediaobject></entry>
	    </row>
	    <row>
	      <entry>Right</entry>
	      <entry>Front</entry>
	    </row>
	  </tbody>
	</tgroup>
      </informaltable>
      
      <para>
	You can also select any azimuth-elevation combination from the Command
	Line. For example, at the prompt type
	
	<command>ae 128 17[Enter]</command>
	
	As with many of the Command Line options, this method of selecting views
	provides a finer degree of control/precision when you need it.
      </para>
      
      <para>
	<application>MGED</application> can also display multiple views simultaneously. Go to the Modes menu
	and select Multipane. Four small panes with different views should
	appear in your Graphics Window, as shown in the following illustration.
      </para>

      <informalfigure>
	<mediaobject>
	  <imageobject>
	    <imagedata align="center" fileref="../../lessons/en/images/mged02_multipane.png" format="PNG"/>
	  </imageobject>
	  <caption>
	    <para>
	      Multipane View of the Radio
	    </para>
	  </caption>
	</mediaobject>
      </informalfigure>      

    </section>

    <section xml:id="shift_grips"><info><title>Working with Shift Grips</title></info>
      
      
      <para>
	The Shift Grip options of <application>MGED</application> are handy hot-key and mouse button
	combinations that can be used in two different ways. With regard to our
	present discussion on viewing, the Shift Grips can, in effect, "drag" the
	world around in front of the viewer (but without actually changing the
	coordinates of the viewed objects). The same Shift Grips can also be used
	in Edit mode to actually move or alter the geometry of your objects. In
	both cases, the Shift Grips appear to do the same thing, so it is
	important always to know the mode in which you are operating.
      </para>
      
      <para>
	In general, the SHIFT key translates (moves), the CTRL key rotates, and
	the ALT key constrains (or limits) translation or rotation to a particular
	axis (x, y, or z). These axes correspond to the three mouse buttons as
	follows: the left button represents the x axis, the middle button
	represents the y axis, and the right button represents the z axis. In
	addition, the SHIFT and CTRL keys can be used in conjunction with any
	mouse button to scale an object (although the ALT key will not constrain
	this action). The following table lists all of the key bindings and their
	functions.
      </para>
      
      <table frame="all">
	<title>Shift Grip Keys and Effects</title>
	
	<tgroup cols="5" align="center" colsep="1" rowsep="1">
	  <colspec colname="c1"/>
	  <colspec colname="c2"/>
	  <colspec colname="c3"/>
	  <colspec colname="c4"/>
	  <thead>
	    <row>
	      <entry>Function</entry>
	      <entry>Key Combination</entry>
	      <entry>Effect in Normal Viewing</entry>
	      <entry>Effect in Edit Mode</entry>
	    </row>
	  </thead>
	  <tbody>
	    <row>
	      <entry>Translate (Move)</entry>
	      <entry>SHIFT + any mouse button + mouse drag</entry>
	      <entry>Moves view in any direction</entry>
	      <entry>Translates object in any direction</entry>
	    </row>
	    <row>
	      <entry>Rotate</entry>
	      <entry>CTRL + any mouse button + mouse drag</entry>
	      <entry>Rotates view in any direction</entry>
	      <entry>Rotates object in any direction</entry>
	    </row>
	    <row>
	      <entry morerows="2" valign="middle">Constrain Translation</entry>
	      <entry>SHIFT + ALT + left mouse button + mouse drag</entry>
	      <entry>Moves view in the x direction</entry>
	      <entry>Translates object in the x direction</entry>
	    </row>
	    <row>
	      <entry>SHIFT + ALT + middle mouse button + mouse drag</entry>
	      <entry>Moves view in the y direction</entry>
	      <entry>Translates object in the y direction</entry>
	    </row>
	    <row>
	      <entry>SHIFT + ALT + right mouse button + mouse drag</entry>
	      <entry>Moves view in the z direction</entry>
	      <entry>Translates object in the z direction</entry>
	    </row>
	    <row>
	      <entry morerows="2" valign="middle">Constrain Rotation</entry>
	      <entry>CTRL + ALT + left mouse button + mouse drag</entry>
	      <entry>Rotates view about the x axis</entry>
	      <entry>Rotates object about the x axis</entry>
	    </row>
	    <row>
	      <entry>CTRL + ALT + middle mouse button + mouse drag</entry>
	      <entry>Rotates view about the y axis</entry>
	      <entry>Rotates object only about the y axis</entry>
	    </row>
	    <row>
	      <entry>CTRL + ALT + right mouse button + mouse drag</entry>
	      <entry>Rotates view about the z axis</entry>
	      <entry>Rotates object aboutthe z axis</entry>
	    </row>
	    <row>
	      <entry>Scale</entry>
	      <entry>SHIFT + CTRL + any mouse button + mouse drag</entry>
	      <entry>Scales view larger or smaller</entry>
	      <entry>Scales object larger or smaller</entry>
	    </row>
	  </tbody>
	</tgroup>
      </table>
      
      <caution>
	<para>
	  Depending on your window manager or desktop environment settings,     
	  some key combinations may already be designated to perform other      
	  tasks (e.g., resizing or moving a window). If so, you may need to     
	  adjust settings to allow the Shift Grip options to function.          
	  Furthermore, left-handed users may have switched the behavior of the  
	  left and right mouse buttons in their system configurations. In such  
	  instances, the terms left mouse button and right mouse button should  
	  be switched throughout this document.                                 
	</para>
      </caution>
      
      <para>
	Probably the easiest way to familiarize yourself with the Shift Grip
	options is to try them out on your radio. Using the preceding table as a
	guide, experiment with translating, rotating, constraining translation and
	rotation to particular axes, and sizing your radio view.
      </para>
      
      <note>
	<para>
	  Remember, although the Shift Grip options may appear to be            
	  manipulating objects, unless you are in Edit mode they are only       
	  manipulating your view of the objects.                                
	</para>
      </note>
    </section>
    
    <section xml:id="learning_viewing_options_review"><info><title>Review</title></info>
      
      
      <para>
	In this lesson, you:
	
	<itemizedlist mark="bullet">
	  <listitem>
	    <para>Created a model radio.</para>
	  </listitem>
	  <listitem>
	    <para>Located  viewing information in the Command Window.</para>
	  </listitem>
	  <listitem>
	    <para>Identified elements of the <application>MGED</application> viewing system.</para>
	  </listitem>
	  <listitem>
	    <para>Viewed your radio from different angles.</para>
	  </listitem>
	  <listitem>
	    <para>Worked with Shift Grips.</para>
	  </listitem>
	</itemizedlist>
      </para>
    </section>
  </article>
