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revision 1.80 by jvk, Thu Feb 13 13:39:30 2003 UTC revision 1.81 by jvk, Thu Feb 13 14:23:20 2003 UTC
# Line 253  can be enumerated: Line 253  can be enumerated:
253  - the view should animate continuously when the focus moves  - the view should animate continuously when the focus moves
254    
255  Furthermore,  Furthermore,
256  It is important to maintain orientation locally,  it is important to maintain orientation locally,
257  that is, going in one direction should result in arriving from  that is, going in one direction should result in arriving from
258  the opposite direction, so that the local spatial structure  the opposite direction, so that the local spatial structure
259  does not change too much.  does not change too much.
# Line 284  because the visual field is wider than i Line 284  because the visual field is wider than i
284  leaving more space at the left and right sides than on the top and bottom.  leaving more space at the left and right sides than on the top and bottom.
285  XXX: left and right hand???  XXX: left and right hand???
286    
287  We choose the geometry as follows:  From the above principles, we have chosen a simple geometry
288    depicted in Fig. [ref-figbuoygeom]_.
289    The buoys are placed on a circle with diameter little less
290    than the screen heighand tcentered at the focus.
291    Thus, the buoys are equally close to the focus, matching
292    the fisheye focus shape.
293    Additionally, a circle arc provides more area for the buoys than,
294    e.g., a straight line.
295    
296    The position of a right-end buoy on the circle is obtained by
297    projecting a line from a constant point on the left side of the view
298    through the anchor point and to the circle, and similarly
299    for the left-end buoys.
300    The resulting layout placed the buoys close to the anchor
301    while maintaining the left-right orientation.
302    Also, such line projections are easy to perceive for humans,
303    because it is analogous to 3D perspective.
304    
305    The buoy scale is chosen to be relative to the anchor's distance
306    from the circle. That is, a buoy anchored at the center of the focus
307    is large and gets linearly smaller as it approaches the circle.
308    
309    Because the documents, even with the fisheye-distortion, can be larger
310    than the buoy circle, buoys anchored far from the focus are drawn
311    near the anchor instead. This is needed to prevent awkward view-cutting
312    long lines and to yield more space for the layout of buoys anchored
313    close to the focus.
314    Furthermore, the final positions of the buoys may need be adjusted
315    to prevent too much overlap.
316    
317    - buoys are placed on a circle centered at the focus and diameter  .. how does this interact with the perception of the projection?
     little less than the screen height  
318    
         - buoys equally close to the focus, matching the fisheye focus shape  
   
         - provides more space for the buoys than, e.g., a straight line  
           (a circle arc is longer)  
   
   - buoys anchored outside the buoy-circle are drawn near the anchor instead,  
     to prevent awkward view-cutting long lines and to yield more space  
     for the layout of buoys anchored closer to the focus  
   
   - the position on the circle is obtained by projecting from a constant  
     point (on left/right) through the anchor to right/left side of the circle  
   
         - buoys placed close to the anchor  
   
         - such line projections are easy to track for humans,  
           because it is analogous to 3d perspective  
   
   - final positions may need be adjusted to prevent too much overlap  
   
         - how does this interact with the perception of the projection?  
   
   - buoy scale is relative to the anchor's distance from the circle  
319    
320  .. raw:: latex  .. raw:: latex
321    
# Line 321  We choose the geometry as follows: Line 326  We choose the geometry as follows:
326     \label{figbuoygeom}     \label{figbuoygeom}
327     Buoy layout geometry: XXX}       Buoy layout geometry: XXX}  
328     \end{figure}     \end{figure}
329    
330       %
331    
332  The above design produces good results and is very simple if not  The above design produces good results and is very simple if not
333  the simplest way to meet the layout requirements.  the simplest way to meet the layout requirements.
334    

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