[HN Gopher] Quaternions, Interpolation and Animation (1998) [pdf]
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       Quaternions, Interpolation and Animation (1998) [pdf]
        
       Author : teleforce
       Score  : 45 points
       Date   : 2023-05-21 13:30 UTC (2 days ago)
        
 (HTM) web link (web.mit.edu)
 (TXT) w3m dump (web.mit.edu)
        
       | tbm57 wrote:
       | These were considered to be satanic black magic when they were
       | first discovered. this is the 'quaternomicon'
        
       | iTokio wrote:
       | 1998
        
       | j2kun wrote:
       | I'm curious what modern animation systems use quaternions. Can
       | anyone who knows graphics well provide references?
        
         | mrcode007 wrote:
         | They're ubiquitous in computer graphics for video games and to
         | some degree in space and aeronautics. They're better than Euler
         | angles because they don't go singular as often. There are other
         | more ansvanced and better parametrizations though.
         | 
         | In space rotations are of critical importance and ensure
         | stability or instability depending on the axis of rotation
        
           | interroboink wrote:
           | > they don't go singular as often
           | 
           | A term I've often heard is "gimbal lock"[1]. Can happen, eg,
           | when a player points the camera straight up, then tries to
           | rotate themselves (depending on how your axes are set up). I
           | don't believe quaternions _ever_ have that particular
           | problem, so not quite sure what is meant by "less often,"
           | here.
           | 
           | [1] https://en.wikipedia.org/wiki/Gimbal_lock
        
             | mrcode007 wrote:
             | You're right, quaternions don't go singular. I
             | misremembered what the problem was. And the problem with
             | the quaternions is that the multiple revolutions will
             | resolve to the same quaternion and then you don't know how
             | many times you've revolved around. For some applications
             | this is important to know.
        
         | Wistar wrote:
         | The Grass Valley Group's late 1980s real-time digital video
         | effects system, the Kaleidoscope, used quaternions for
         | orientation of 2D planes in 3D space (Cartesian) to avoid
         | gimbal lock although it also offered Euler angles for animation
         | of multiple rotations.
        
         | omoikane wrote:
         | Many game engines has first class support for quaternions, for
         | example Godot:
         | 
         | https://docs.godotengine.org/en/stable/classes/class_quatern...
        
       | gatane wrote:
       | The answer to slerp is to slerp over slerp
        
       | sxp wrote:
       | It's somewhat silly to read about animation using a static doc.
       | My preferred intro to quaternions in the context of motion is the
       | pair of articles at https://acko.net/tag/quaternions/. They were
       | critical helping me learn quaternions for computer graphics. I
       | also recommend https://acko.net/blog/how-to-fold-a-julia-fractal/
       | as a primer if you aren't comfortable with regular complex
       | numbers.
        
         | Culonavirus wrote:
         | That site is pretty amazing.
        
       | admsmz wrote:
       | Geometric Algebra subsumes and extends quaternions:
       | 
       | https://www.youtube.com/watch?v=60z_hpEAtD8
        
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