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    1 \chapter{TUTORIALS ON VIEWING AND STATES}
    2 
    3 Tutorials with illustrations are provided to give the MGED user a
    4 step-by-step walk-through of the basic capabilities of the graphics
    5 editor.
    6 Standard UNIX login and logout procedures appropriate to each site
    7 should be followed prior to
    8 beginning and after ending the tutorials.
    9 
   10 Each of the tutorials will use the solids contained the MGED database called
   11 ``prim.g''.
   12 These can be obtained by making a copy of ``db/prim.g''
   13 from the BRL-CAD Package distribution tree.  It is important to make
   14 a copy of the database and work with that, rather than using the
   15 supplied one.  Changes made during the editing process are written
   16 to the database when they are {\sl accepted}.
   17 
   18 The first tutorial shows a sample invocation dialogue.  All other
   19 tutorials start at the first MGED prompt ({\tt mged> }). If the user
   20 wishes to continue from one tutorial to the next without leaving MGED,
   21 issue the {\em press reject} and {\em press reset} commands
   22 before starting a new tutorial.
   23 User input will be shown in an
   24 {\em emphasized} font, and MGED output will appear in a {\tt typewriter}
   25 font.  If the user input is shown on the same line as a prompt, the
   26 input is literal.  If the user input is shown on a line by itself,
   27 it is a directive, and is entered in an appropriate fashion.
   28 
   29 The tutorials are self-contained, and if the user wishes to proceed to
   30 the next tutorial without exiting MGED,
   31 the RESET button should be pressed
   32 to return to the top view, where the model XYZ axes
   33 map to the screen XYZ axes.
   34 
   35 The standard recovery procedure when in the middle of an editing operation
   36 is to select REJECT edit.  Control is
   37 returned to the viewing state, and the user can restart with the last edit (e)
   38 command used in the tutorial.
   39 
   40 \section{States Within the Edit Process}
   41 
   42 In this tutorial, the user will invoke MGED on a file called ``prim.g'';
   43 attach a {\sl display manager\/}; explore the various MGED states;
   44 and finally, exit MGED.  A MGED database has a treelike structure.  The
   45 leaves are the individual solids, and the other nodes are groupings
   46 of those solids.  The solid editing functions are concerned with defining
   47 and modifying the leaves, and the object editing functions operate
   48 on groups, which are Boolean combinations of solids.  One useful mental
   49 model is to envision solid editing as operating directly on a leaf and
   50 object editing as operating on the arc connecting a pair of nodes.  The
   51 object edit will affect everything below the selected arc (this is why
   52 there is an additional state transition when object editing).
   53 
   54 \section{Viewing State}
   55 
   56 The first task is to invoke MGED.  This tutorial will assume the user
   57 has a copy of the ``prim.g'' database in the current directory.
   58 
   59 \noindent
   60 {\tt \$ }{\em mged prim.g}\\
   61 {\tt BRL-CAD Release 3.0 Graphics Editor (MGED) Compilation 82}\\
   62 {\tt Thu Sep 22 08:08:39 EDT 1988}\\
   63 {\tt mike@video.brl.mil:/cad/.mged.4d2}\\
   64 
   65 \noindent
   66 {\tt attach (nu|tek|tek4109|ps|plot|sgi)[nu]? }{\em sgi}\\
   67 {\tt ATTACHING sgi (SGI 4d)}\\
   68 {\tt Primitive Objects (units=mm)}\\
   69 {\tt mged> }\\
   70 
   71 The first three lines give information about which version of MGED is running,
   72 when it was compiled, and who compiled it.  The next line is the display
   73 manager attach prompt.  This prompt provides a list of available display
   74 managers, then shows what the default will be (selected if the user answers
   75 with a carriage return).  In this case, the Silicon Graphics 4d display
   76 manager was selected, as is noted by the following line.
   77 Next the title of the database and
   78 the unit of measurement used in the database are printed,
   79 and finally, the first prompt is issued.
   80 At this point MGED has loaded ``prim.g''; attached the SGI display;
   81 and is awaiting commands.  Attaching a display also causes what
   82 is known as the MGED {\sl faceplate} to be drawn on the graphics display.
   83 
   84 The faceplate has several features of interest.  In the upper left corner
   85 of the display, is a box which always shows the current MGED {\sl state}.
   86 This can be one of six states:  {\bf VIEWING}, {\bf SOL PICK},
   87 {\bf SOL EDIT}, {\bf OBJ PICK}, {\bf OBJ PATH}, or {\bf OBJ EDIT}.
   88 
   89 Immediately below, is the menu area.  The only menu item initially shown is
   90 one labeled {\bf BUTTON MENU}.  This menu item toggles the display of the
   91 button menu entries when {\sl selected} (more on selection later).
   92 
   93 At the bottom of the display are two status lines.  The first line
   94 contains information about the current view.
   95 The entry labeled {\bf cent=} gives the {\sl model space} coordinates
   96 of the dot in the center of the display.
   97 The entry labeled {\bf sz=} reflects the current size in model units of
   98 the {\sl viewing cube}.  The viewing cube is a mathematical construct
   99 centered on the dot in the center of the display.  The {\bf ang=}
  100 display shows the current rate of rotation in each of the three axes.
  101 The bottom line is used for several kinds of information.
  102 In the {\bf VIEWING} state, it displays the title of the database.
  103 
  104 The MGED viewing features are designed to allow the user to examine
  105 models at different angles.
  106 Preset views can be invoked at
  107 anytime by using either the menu or the button box.
  108 Selecting a preset view does
  109 not change the coordinates of the primitives,
  110 but instead changes the angle from which these primitives are
  111 displayed.  Five standard views (top, right, front, 35/25, and 45/45) can
  112 be obtained by using either the bottom menu on the display screen or the
  113 control box.
  114 Three additional views (button, left, and rear) can be obtained
  115 by using the button box, but not by using the menu.
  116 
  117 The normal or default viewing state is the ``top'' orientation,
  118 with model +X pointing towards the right of the screen,
  119 model +Y pointing towards the top of the screen,
  120 and model +Z pointing out of the screen.
  121 In the ``top'' view, the model and screen axes are the same.
  122 The ``reset'' button and ``Reset Viewsize'' menu items also
  123 result in a ``top'' view.
  124 
  125 The following table shows the angles of rotation to obtain the other views.
  126 \begin{tabular}{l l}
  127 View    &            Angle of Rotation (from top) \\
  128  \\
  129 Top      &                     0, 0, 0 \\
  130 Bottom   &                   180, 0, 0 \\
  131 Right    &                   270, 0, 0 \\
  132 Left     &                  270, 0, 180 \\
  133 Front    &                  270, 0, 270 \\
  134 Rear     &                  270, 0, 90 \\
  135 35, 25   &                  295, 0, 235 \\
  136 \end{tabular}
  137 
  138 \noindent
  139 {\tt mged>\ }{\em e arb8}\\
  140 {\tt vectorized in 0 sec}\\
  141 {\tt mged>\ }{\em size 12}\\
  142 {\tt mged> }\\
  143 
  144 \begin{figure}
  145 \centering \includegraphics{t1-top-vw.ps}
  146 \caption{``arb8'' Top View.}
  147 \label{t1-top-vw}
  148 \end{figure}
  149 
  150 The {\bf e} command causes the named object(s) -- a solid named ``arb8''
  151 in this case
  152 -- to be displayed, and the {\bf size} command sets the size of the
  153 viewing cube. Figure \ref{t1-top-vw} shows what the display currently
  154 looks like.  In this view, the X-axis is to the right, the Y-axis points
  155 up, and the Z-axis is perpendicular to (poking out of) the screen.
  156 
  157 \noindent
  158 {\em Twist the {\bf Y ROT} knob clockwise and back.}\\
  159 {\em Twist the {\bf X ROT} knob counterclockwise and back.}\\
  160 
  161 These knobs, along with the {\bf Z ROT} knob, rotate the viewing cube.
  162 Use of the rotation
  163 knobs allows the user to view the model from any orientation.
  164 Turning a knob clockwise causes a rotation in the positive direction,
  165 while turning a knob counterclockwise causes a negative rotation
  166 (right-hand rule).  The knobs are rate based, not position based;
  167 once a rotation has been started, it will continue until the
  168 knob is returned to zero (or the {\bf zeroknobs} button is pressed).
  169 Rotations are about the viewing cube (screen) axes, not the model axes.
  170 Systems without knobs can use the {\bf knob} command.
  171 
  172 \noindent
  173 {\em Move the mouse (or pen) until the cursor is in the {\bf BUTTON MENU}
  174 block and then press the middle mouse button (depress the pen).}\\
  175 
  176 \begin{figure}
  177 \centering \includegraphics{t1-rot-vw.ps}
  178 \caption{``arb8'' Rotated View.}
  179 \label{t1-rot-vw}
  180 \end{figure}
  181 
  182 Pressing the middle mouse button (or the pen) {\sl selects} something.
  183 When the cursor is inside the menu area, a selection
  184 causes the event described by the menu item to occur.
  185 Selecting {\bf BUTTON MENU} causes the button menu to appear on the left
  186 side of the screen. The {\bf BUTTON MENU} menu item is
  187 a toggle; subsequent selection of this item will cause the button menu
  188 to disappear.
  189 Figure \ref{t1-rot-vw} shows the new display.
  190 
  191 \noindent
  192 {\em Move the cursor from the menu area to a point near the
  193 upper left corner of the solid and select it (press the center mouse
  194 button).}\\
  195 
  196 In the {\bf VIEWING} state, making a selection while outside of the menu
  197 area will move the selected point to the center of the display.  Look
  198 carefully at the center of the display; the point just selected is now
  199 located at the center dot. Use the {\bf center} command to reset any
  200 translations made with the mouse.
  201 
  202 \noindent
  203 {\tt mged> }{\em center 0 0 0}\\
  204 {\tt mged> }\\
  205 
  206 From the {\bf VIEWING} state, the user will normally transition to either the
  207 {\bf SOL PICK} or {\bf OBJ PICK} state.
  208 The {\bf SOL PICK} state is selected by:
  209 \begin{itemize}
  210 \item Selecting the {\bf Solid Illum} button menu entry, or,
  211 \item Pressing the {\bf sill} button (this button may be labeled
  212 using some variation of ``Solid Illum''), or,
  213 \item Typing {\bf press sill}.
  214 \end{itemize}
  215 Similar entries ({\bf Object Illum}) and ({\bf oill}) exist for transitioning
  216 into the {\bf OBJ PICK} state.
  217 In general, the {\bf press} command is the basic mechanism (type
  218 {\bf press help} for a list of available commands).  Most of the press
  219 commands have been mapped onto a button box if it is available,
  220  and some of the
  221 most common are also mapped into the {\bf BUTTON MENU} so they can
  222 accessed without letting go of the mouse.
  223 
  224 \section{Solid Pick State}
  225 
  226 \noindent
  227 {\em Place MGED in the {\bf SOL PICK} state using one of the
  228 above mechanisms.}\\
  229 
  230 \begin{figure}
  231 \centering \includegraphics{t1-sol-pk.ps}
  232 \caption{MGED In Solid Pick State.}
  233 \label{t1-sol-pk}
  234 \end{figure}
  235 
  236 Upon entering the {\bf SOL PICK} state, the display will look similar to
  237 Figure \ref{t1-sol-pk}.  The {\bf SOL PICK} state used to select which
  238 of the displayed solids is to be edited.  Note that the color of the
  239 solid has changed from red to white.  The screen is divided into as many
  240 horizontal zones as there are solids displayed, and each zone is
  241 assigned to one solid.  As the mouse is moved vertically through each
  242 zone, the corresponding solid is highlighted (``illuminated'') by
  243 drawing it in white.   In this instance, there is only one solid being
  244 displayed, so this state is relatively uninteresting.
  245 If the system being used has no mouse, there is no reason to enter the
  246 {\bf SOL PICK} state.  The user will instead transition directly to
  247 the {\bf SOL EDIT} state using the {\bf sed} command.
  248 
  249 \noindent
  250 {\tt mged> }{\em press reject}\\
  251 {\tt mged> }{\em e ellg}\\
  252 {\tt mged> }\\
  253 {\em Press the {\bf sill} button}\\
  254 
  255 \begin{figure}
  256 \centering \includegraphics{t1-2s-pk.ps}
  257 \caption{MGED In Solid Pick with Two Solids.}
  258 \label{t1-2s-pk}
  259 \end{figure}
  260 
  261 Note that the first action taken was to {\sl reject} the edit.  Any time MGED
  262 is not in the {\bf VIEWING} state, a {\sl reject} command (via
  263 {\bf press}, button, or mouse) discards all editing changes accumulated
  264 since the last transition out of the {\bf VIEWING} state, and places
  265 MGED in the {\bf VIEWING} state.
  266 The display should now look similar to Figure \ref{t1-2s-pk}.
  267 Notice that one solid is white and
  268 the name of that solid is displayed in the upper left corner of the
  269 display, as well as in the bottom status line. The solid to be edited is
  270 selected by moving the mouse up and down until the zone corresponding to
  271 the desired solid is reached. Once the appropriate zone is reached, select it.
  272 This selects a solid, and once a solid is selected,
  273 MGED enters the {\bf SOL EDIT} state.
  274 
  275 \section{Solid Edit State}
  276 
  277 \noindent
  278 {\tt mged> }{\em d ellg}\\
  279 {\tt mged> }\\
  280 {\em Select the solid called ``arb8''.}\\
  281 
  282 \begin{figure}
  283 \centering \includegraphics{t1-sol-ed.ps}
  284 \caption{Solid Edit State.}
  285 \label{t1-sol-ed}
  286 \end{figure}
  287 
  288 The {\bf d} command removes something from the display.  In this
  289 case, the solid ``ellg'' was removed to reduce clutter.
  290 The display should now look like Figure \ref{t1-sol-ed}.
  291 When MGED enters the solid edit state, the following occurs:
  292 \begin{itemize}
  293 \item The solid selected for editing remains illuminated,
  294 \item The solid is labeled,
  295 \item The coordinates (or dimensions) associated with the labels,
  296 and other information is displayed to the right of the menu area,.
  297 \item If the solid is a member of one or more groups, a similar set
  298 of coordinates called the {\sl PATH} is displayed immediately below
  299 the first set of coordinates,
  300 \item The {\bf *SOLID EDIT*} menu is displayed, and,
  301 \item A solid specific edit menu (in this case the {\bf ARB MENU})
  302 is displayed.
  303 \end{itemize}
  304 
  305 The {\bf *SOLID EDIT*} menu provides access to generic operations (translation, rotation
  306 and scaling) common to all solids.
  307 The solid specific edit menu is a list of solid type specific editing operations.
  308 Selecting one of the solid specific edit menus causes a submenu with solid type specific
  309 choices to be displayed.  To remove this submenu, select either the
  310 {\bf RETURN} item in the submenu, or the {\bf edit menu} item in the
  311 {\bf *SOLID EDIT*} menu.
  312 
  313 It is in this state that the solid is altered to meet the modeler's
  314 requirements. The shape, positioning, and orientation of the solid is
  315 changed using numeric keyboard input, positioning of the mouse, or by
  316 use of the knobs.  Once the solid has been altered, the edit is
  317 either accepted or rejected.  Accepting the edit causes all changes
  318 made to be written to the database; rejecting the edit ``throws them
  319 away''. Either operation will terminate the edit session and return MGED
  320 to the {\bf VIEWING} state.
  321 
  322 \noindent
  323 {\em Reject the edit.}\\
  324 
  325 \section{Object Pick State}
  326 
  327 \noindent
  328 {\em Place MGED in the {\bf OBJ PICK} state.}\\
  329 
  330 \begin{figure}
  331 \centering \includegraphics{t1-obj-pk.ps}
  332 \caption{Object Pick State.}
  333 \label{t1-obj-pk}
  334 \end{figure}
  335 
  336 Figure \ref{t1-obj-pk} shows what the display looks like when in the
  337 {\bf OBJ PICK} state. As with the {\bf SOL PICK} state, a single solid is
  338 selected.  This solid becomes the reference solid for the object edit.
  339 In the {\bf OBJ PICK} state, the solid will be shown
  340 as a member of one or more objects.  Less obvious is the fact that the
  341 local axes associated with the selected solid are the axes used for the
  342 entire object during the object edit.
  343 
  344 \section{Object Path State}
  345 
  346 \noindent
  347 {\em Select ``arb8''.}\\
  348 
  349 \begin{figure}
  350 \centering \includegraphics{t1-obj-ph.ps}
  351 \caption{Object Path Selection State.}
  352 \label{t1-obj-ph}
  353 \end{figure}
  354 
  355 MGED transitions into the {\bf OBJ PATH} state once a solid has been
  356 picked from {\bf OBJ PICK}. Figure \ref{t1-obj-ph} is the display in
  357 the {\bf OBJ PATH} state.  When in this state the extent of the editing
  358 operation is set.  Everything below the editing point is affected by the
  359 edit.  The editing point is shown by the {\sl MATRIX} label in the
  360 display.  It is shown as {\bf [MATRIX]} in the upper left part of the
  361 display and as {\bf \_\_MATRIX\_\_} in the second status line.  The editing
  362 point is chosen with the same mechanism used by {\bf SOL PICK} and
  363 {\bf OBJ PICK}.  This time, there is one horizontal zone for each node in
  364 the path between the root and selected leaf.  Moving the mouse up and down
  365 moves the editing point up and down in the tree.  Once again, having a
  366 simple database and only one object in view makes for a relatively
  367 uninteresting situation.
  368 
  369 \section{Object Edit State}
  370 
  371 \noindent
  372 {\em Select the editing point above ``arb8''.}\\
  373 
  374 \begin{figure}
  375 \centering \includegraphics{t1-obj-ed.ps}
  376 \caption{Object Edit State.}
  377 \label{t1-obj-ed}
  378 \end{figure}
  379 
  380 MGED is now in the {\bf OBJ EDIT} state and the display should look like
  381 Figure \ref{t1-obj-ed}.
  382 When MGED enters the object edit state, the following occurs:
  383 \begin{itemize}
  384 \item The reference solid remains illuminated,
  385 \item The reference solid is labeled,
  386 \item The information associated with the labels is displayed to the right
  387 of the menu area, and
  388 \item The {\bf *OBJ EDIT*} menu is displayed.
  389 \end{itemize}
  390 
  391 The {\bf OBJ EDIT} state is used to modify the
  392 Homogeneous Transform Matrix selected during the {\bf OBJ PATH} state.
  393 Permissible operations include uniform and affine scaling of the objects,
  394 as well as translation and rotation.
  395 As with the {\bf SOL EDIT} state, MGED accepts changes entered using
  396 the keyboard, mouse or knobs.
  397 
  398 This concludes the first tutorial.  Examples of the appearance of MGED
  399 in each of the six states have been given, along with some idea of what
  400 each of the states is used for.  All that remains is to reject the current
  401 edit, and exit MGED.  Strictly speaking the {\bf q} command could be entered
  402 directly, but doing so, can become a dangerous habit.
  403 
  404 \noindent
  405 {\em Select {\bf REJECT Edit} using the mouse.}\\
  406 {\em Press the {\bf reject} button.}\\
  407 {\tt mged> }{\em d arb8}\\
  408 {\tt mged> }{\em q}\\
  409 {\tt \$ }\\
  410 
  411 \section{Editing in the Plane of the Screen}
  412 \begin{figure}
  413 \centering \includegraphics{plane-top1.ps}
  414 \caption{A Top View of the Coordinate Axes.}
  415 \label{plane-top1}
  416 \end{figure}
  417 
  418 When MGED is in a ``translate'' mode within an edit state,
  419 the plane of the mouse or data tablet is mapped to
  420 the plane of the screen, to permit moving objects in a
  421 controlled way in two of the three available dimensions.
  422 The orientation of the plane of the screen is determined by the
  423 currently selected view.
  424 In most circumstances, users will find that repositioning objects
  425 is easiest when the plane of the screen is oriented in an
  426 axis-aligned view.  This is most easily accomplished by utilizing
  427 one of the preset views.
  428 For this exercise, obtain a copy of the {\em axis.g} database,
  429 and run MGED, e.g.:
  430 
  431 \noindent{\tt
  432 \$ cp db/axis.g . \\
  433 \$ mged axis.g \\
  434 BRL-CAD Release 3.0 Graphics Editor (MGED) Compilation 82 \\
  435     Thu Sep 22 08:08:39 EDT 1988 \\
  436     mikel@video.br:/cad/.mged.4d2 \\
  437 \\
  438 attach (nu|tek|tek4109|ps|plot|sgi)[nu]? {\em sgi} \\
  439 ATTACHING sgi (SGI 4d) \\
  440 X,Y,Z Coordinate Axis  (units=none) \\
  441 mged> {\em e axis} \\
  442 vectorized in 0 sec \\
  443 {\em Select ``Top'' in the Button menu} \\
  444 mged> \\
  445 }
  446 
  447 \subsection{Top View}
  448 \begin{figure}
  449 \centering \includegraphics{plane-top2.ps}
  450 \caption{Translating from the Top View.}
  451 \label{plane-top2}
  452 \end{figure}
  453 
  454 The top view is the default view.  The orientation of the axes
  455 is shown in Figure \ref{plane-top1}.
  456 The surface of the viewing screen and the graphics tablet is the XY plane.
  457 Edit changes using the graphics tablet will affect only the X and Y
  458 coordinates of the primitive.
  459 
  460 \noindent{\tt
  461 mged> {\em sed x} \\
  462 {\em Select ``Translate'' in the Solid Edit menu} \\
  463 mged>
  464 }
  465 
  466 Select different points on the tablet with the mouse, each time
  467 pressing the middle mouse button.
  468 Notice how the X and Y coordinates of the V vector change,
  469 but the Z coordinate does not.
  470 An example of this is shown in Figure \ref{plane-top2};
  471 compare the values of V with those in Figure \ref{plane-top1}.
  472 
  473 {\em Select ``REJECT Edit'' in the Button menu}
  474 
  475 \subsection{Bottom View}
  476 \begin{figure}
  477 \centering \includegraphics{plane-bot1.ps}
  478 \caption{A Bottom View of the Coordinate Axes.}
  479 \label{plane-bot1}
  480 \end{figure}
  481 \begin{figure}
  482 \centering \includegraphics{plane-bot2.ps}
  483 \caption{Translating from the Bottom View.}
  484 \label{plane-bot2}
  485 \end{figure}
  486 
  487 \noindent{\tt
  488 mged> {\em press bottom} \\
  489 mged> {\em sed x} \\
  490 {\em Select ``Translate'' in the Solid Edit menu} \\
  491 mged>
  492 }
  493 
  494 The {\em press bottom} command selects the bottom view of the
  495 model, and the new configuration of the axes can be seen in
  496 Figure \ref{plane-bot1}.
  497 The surface of the viewing screen and the mouse or tablet
  498 are still in the XY plane.
  499 Edit changes using the graphics tablet will affect only the X and Y
  500 components of the solid.
  501 Select different points on the tablet with the mouse and notice the
  502 changes in the coordinates;
  503 compare the values of V with those in Figure \ref{plane-bot2}.
  504 
  505 {\em Select ``REJECT Edit'' in the Button menu}
  506 
  507 \subsection{Right View}
  508 \begin{figure}
  509 \centering \includegraphics{plane-right1.ps}
  510 \caption{A Right View of the Coordinate Axes.}
  511 \label{plane-right1}
  512 \end{figure}
  513 \begin{figure}
  514 \centering \includegraphics{plane-right2.ps}
  515 \caption{Translating from the Right View.}
  516 \label{plane-right2}
  517 \end{figure}
  518 
  519 \noindent{\tt
  520 {\em Select ``Right'' in the Button menu} \\
  521 mged> {\em sed x} \\
  522 {\em Select ``Translate'' in the Solid Edit menu} \\
  523 mged>
  524 }
  525 
  526 The right hand view has been selected. Model +X still proceeds to the right,
  527 but now model +Z is at the top of the screen, and model +Y is
  528 pointing out of the screen.
  529 This new configuration is depicted in Figure \ref{plane-right1}.
  530 The surface of the viewing screen and the graphics tablet is the XZ plane.
  531 Edit changes using the graphics tablet will affect only the X and Z
  532 coordinates of the solid.
  533 Select different points on the tablet with the mouse and notice the
  534 changes in the V coordinates;  only the X and Z components change,
  535 as in Figure \ref{plane-right2}.
  536 
  537 {\em Select ``REJECT Edit'' in the Button menu}
  538 
  539 \subsection{Front View}
  540 \begin{figure}
  541 \centering \includegraphics{plane-front1.ps}
  542 \caption{A Front View of the Coordinate Axes.}
  543 \label{plane-front1}
  544 \end{figure}
  545 \begin{figure}
  546 \centering \includegraphics{plane-front2.ps}
  547 \caption{Translating from the Front View.}
  548 \label{plane-front2}
  549 \end{figure}
  550 
  551 \noindent{\tt
  552 {\em Select ``Right'' in the Button menu} \\
  553 mged> {\em sed x} \\
  554 {\em Select ``Translate'' in the Solid Edit menu} \\
  555 mged>
  556 }
  557 
  558 The front view has been selected.  Model +X points out of the screen,
  559 model +Y points to the right, and model +Z points towards the top
  560 of the screen, as shown in Figure \ref{plane-front1},
  561 which has been slightly rotated off the preset view to improve
  562 the legibility of the axis labels.
  563 The surface of the viewing screen and the graphics tablet is the YZ
  564 plane.  Edit changes will affect only the Y and Z
  565 coordinates of the primitive, as shown in Figure \ref{plane-front2}.
  566 Select different points on the tablet with the mouse and notice the
  567 changes in the coordinates.
  568 
  569 {\em Select ``REJECT Edit'' in the Button menu}
  570 
  571 \subsection{35, 25 View}
  572 \begin{figure}
  573 \centering \includegraphics{plane-35a.ps}
  574 \caption{An Oblique 35,25 View of the Coordinate Axes.}
  575 \label{plane-35a}
  576 \end{figure}
  577 \begin{figure}
  578 \centering \includegraphics{plane-35b.ps}
  579 \caption{Translating in the 35,25 View.}
  580 \label{plane-35b}
  581 \end{figure}
  582 
  583 \noindent{\tt
  584 {\em Select ``35,25'' in the Button menu} \\
  585 mged> {\em sed x} \\
  586 {\em Select ``Translate'' in the Solid Edit menu} \\
  587 mged>
  588 }
  589 
  590 Figure \ref{plane-35a} is the 35,25 view of the axes model.
  591 The axes are no longer
  592 parallel or perpendicular to the viewing surface or to the graphics tablet.
  593 Edit changes using the graphics tablet will affect all of the coordinates of
  594 the solid, in a manner that is visually intuitive when the solid
  595 is moved around on the screen.
  596 Select different points on the tablet with the mouse and notice the
  597 changes in the coordinates, such as in Figure \ref{plane-35b}.
  598 Note how all three components of the V vector have changed.
  599 
  600 {\em Select ``REJECT Edit'' in the Button menu}