[HN Gopher] Fixing the Drift in Shape Rotations
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       Fixing the Drift in Shape Rotations
        
       Author : steveruizok
       Score  : 21 points
       Date   : 2021-11-19 14:19 UTC (8 hours ago)
        
 (HTM) web link (www.steveruiz.me)
 (TXT) w3m dump (www.steveruiz.me)
        
       | xvedejas wrote:
       | There should also be strategies for the choice of center to be
       | invariant even after re-selecting the rotated set of shapes. You
       | should be able to do this by finding the two points farthest from
       | each other, and choosing the midpoint between the two, for
       | instance. But that point might not be unique, so maybe finding
       | the center of the smallest circle enclosing all objects would be
       | a better example?
        
       | _dain_ wrote:
       | >However, the rotated shapes probably have a different average
       | center; which means that your second rotation (ie to rotate
       | things back) is pivoting around a different point. And that's
       | what causes the change of position.
       | 
       | Uhh, what? Why doesn't the rotated group have the same centre as
       | the original? The article glosses right over this without
       | explaining it. Is it floating point imprecision? Is it from
       | rasterization?
        
         | [deleted]
        
         | glenjamin wrote:
         | I think it's because the centre is computed using the X and Y
         | axis, and the rotated shapes have a different bounding box on
         | those axes.
        
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       (page generated 2021-11-19 23:00 UTC)