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revision 1.107 by tjl, Fri Feb 14 17:12:16 2003 UTC revision 1.108 by tjl, Fri Feb 14 19:30:21 2003 UTC
# Line 342  define an ellipse somewhat smaller than Line 342  define an ellipse somewhat smaller than
342  and if the buoy would be inside this ellipse, its position  and if the buoy would be inside this ellipse, its position
343  and size is calculated differently.  and size is calculated differently.
344    
345  The size falls  The position is calculated by *projecting* the anchor to the circle
346    from the leftmost point of the ellipse.
347    This places the buoys in a predictable and comprehensible way:
348    the human eye is good at understanding pencils of lines, due to perspective.
349    The size of the projected buoys
350    falls linearly with the distance of the anchor from the
351    center up to the edge of the ellipse,
352    
353    For left-link-end buoys the preceding discussion should
354    be reversed.
355    
356    ..  Thus, the buoys are equally close to the focus, matching
357        the fisheye focus shape.
358        Additionally, a circle arc provides more area for the buoys than,
359        e.g., a straight line.
360    
 The buoys are placed on an ellipse with diameter little less  
 than the screen heighand tcentered at the focus.  
 Thus, the buoys are equally close to the focus, matching  
 the fisheye focus shape.  
 Additionally, a circle arc provides more area for the buoys than,  
 e.g., a straight line.  
   
 The position of a right-end buoy on the circle is obtained by  
 projecting a line from a constant point on the left side of the view  
 through the anchor point and to the circle, and similarly  
 for the left-end buoys.  
361  The resulting layout placed the buoys close to the anchor  The resulting layout placed the buoys close to the anchor
362  while maintaining the left-right orientation.  while maintaining the left-right orientation.
363  Also, such line projections are easy to perceive for humans,  If buoy anchors coincide or are very close to each other
364  because it is analogous to 3D perspective.  in the focused node,
365    the final positions of the buoys need be adjusted to prevent.
 The buoy scale is chosen to be relative to the anchor's distance  
 from the circle. That is, a buoy anchored at the center of the focus  
 is large and gets linearly smaller as it approaches the circle.  
   
 Because the documents, even with the fisheye-distortion, can be larger  
 than the buoy circle, buoys anchored far from the focus are drawn  
 near the anchor instead (while maintaining the link direction).  
 This is needed to prevent awkward view-cutting  
 long lines and to yield more space for the layout of buoys anchored  
 close to the focus.  
 Furthermore, the final positions of the buoys may need be adjusted  
 to prevent too much overlap.  
366    
367  .. how does this interact with the perception of the projection?  .. how does this interact with the perception of the projection?
368    
# Line 381  to prevent too much overlap. Line 372  to prevent too much overlap.
372        
373     Buoy layout geometry: XXX     Buoy layout geometry: XXX
374    
 The above design produces good results and is very simple if not  
 the simplest way to meet the layout requirements.  
   
   
   
375    
376    
377  Paper  Paper
378  -----  -----
379    
380  Although the silhuettes of the buoys are different,  The fragments of nodes seen in buoys are
381  the fragments of the documents still seem quite similar.  generally very similar in appearance.
382  The user could identify the related documents by  The user could identify the related documents by
383  reading the text of a fragment, but that requires attention.  reading the text of a fragment, but that requires attention.
384    

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