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revision 1.105 by tjl, Fri Feb 14 16:56:59 2003 UTC revision 1.106 by tjl, Fri Feb 14 17:08:03 2003 UTC
# Line 229  three simple principles [XXXrefs???]: Line 229  three simple principles [XXXrefs???]:
229    to go back, without a "back button" [implies bidirectional links]    to go back, without a "back button" [implies bidirectional links]
230    "once you get there, you should see how you can get back".    "once you get there, you should see how you can get back".
231    
232    There is one scrollable focus node ("current document"),
233    and links
234    
235  To be able to show all the link targets near the focus,  To be able to show all the link targets near the focus,
236  only the *relevant fragments* (the immediate surroundings of the other  only the *relevant fragments* (the immediate surroundings of the other
237  end of the link) of the target nodes can be shown.  end of the link) of the target nodes can be shown.
# Line 291  For the layout of the buoys we give the Line 294  For the layout of the buoys we give the
294  - the view should animate continuously when the focus moves  - the view should animate continuously when the focus moves
295  - the user should be able to understand and predict the motion  - the user should be able to understand and predict the motion
296    of the buoys.    of the buoys.
297    - there should be little or no hysteresis
298  - buoys should be placed close to their anchors  - buoys should be placed close to their anchors
299    - time coherence: when traversing a link, i.e. animating a buoy into focus,
300      the former focused node should have a clear relationship.
301    
302  Furthermore,  The apparent conflict between "no hysteresis" and "time coherence"
303  it is important to maintain orientation locally,  can be resolved by maintaining a local spatial structure
304  that is, going in one direction should result in arriving from  by giving each link a specific left-right orientation
305  the opposite direction, so that the local spatial structure  so that a right-end node and left-end node retain their relative
306  does not change too much.  locations w.r.t. to the link
307    independent of either of them being the main node.
308  This matches the way the brain understands space  This matches the way the brain understands space
309  as globally distorted, segmented, locally Euclidian views  as globally distorted, segmented, locally Euclidian views
310  (see, e.g. [wang01mindsviews]_).  (see, e.g. [wang01mindsviews]_).
311    
312    ..  it is important to maintain orientation locally,
313        that is, going in one direction should result in arriving from
314        the opposite direction, so that the local spatial structure
315        does not change too much.
316    
317  .. http://acad88.sahs.uth.tmc.edu/research/publications/iccs2001spatial.pdf  .. http://acad88.sahs.uth.tmc.edu/research/publications/iccs2001spatial.pdf
318  .. http://citeseer.nj.nec.com/hunt99orientation.html  .. http://citeseer.nj.nec.com/hunt99orientation.html
319    
 Because of this, each link has a specific left-right orientation  
 so that a right-end buoy is drawn on the right side of the view  
 and a left-end buoy on the left side.  
   
320  More than two opposing directions could also be used, but  More than two opposing directions could also be used, but
321  is is not required for the local spatial coherence and it would also  is is not required for the local spatial coherence and it would also
322  limit the layout of a large number of buoys.  limit the layout of a large number of buoys.
323  Furthermore, there is usually no meaningful global 2D layout for  Furthermore, there is usually no meaningful global 2D layout for
324  a network of nodes, so the extra directions would not help much  a network of nodes, so the extra directions would not help much
325  in perceiving the position in the global structure.  in perceiving the position in the global structure.
 In our application, the structure has simply directed links,  
 visualized as the left-right direction of the connection lines.  
326    
327  As for the horizontal orientation of the link direction,  Orienting the link direction horizontally
328  it is more natural than vertial,  rather than vertically is more natural
329  because the visual field is wider than it is tall  because the visual field is wider than it is tall ---
330  (as exemplified by the usual screen aspect ratios of 4:3 and 16:9)  consider the usual screen aspect ratios of 4:3 and 16:9.
331  leaving more space at the left and right sides than on the top and bottom.  
332  XXX: left and right hand???  ..  leaving more space at the left and right sides than on the top and bottom.
333        XXX: left and right hand???
334    
335  From the above principles, we have chosen a simple geometry  From the above principles, we have chosen a simple geometry
336  depicted in Fig. [ref-figbuoygeom]_.  depicted in Fig. [ref-figbuoygeom]_.

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