On 3-10-2018 2:34, Kenneth wrote:
> To take a break from my other POV-ray chores, I made a simple animated demo of
> what an object looks like when it rotates (in POV-ray), as if free-falling under
> gravity-- but discounting wind resistance or any other extra force. Its a
> comparison between applying the rotations in two axes vs. three. I made the
> animation my own purposes (to easily refer to later), but it might be of
> interest to others as well.
> 
> There's an obvious difference in the visual appearence of the objects. My own
> preference is for the 'two-rotation' scheme; it just looks more 'natural' (or
> more 'expected'?) Using all three rotation axes imparts an 'extra' force to the
> object-- kind of like wind resistance (which is also interesting, of course, but
> otherwise kind of strange.) The 3-axis scheme *might* also depend on the order
> of how those rotations are applied, to look 'more correct'-- not just straight
> <x,y,z>, in other words.
> 
> Long ago, I originally thought that a free-falling object needed all three
> rotations to look natural. The idea seemed logical-- but the visual result
> didn't bear that out (to my eyes, anyway.) I guess I could do a thorough
> analysis of the applied 'vector forces' that cause an object to rotate in the
> first place -- but that's a lot of work  ;-)  For now, I'm curious as to which
> scheme you prefer, from a purely visual standpoint.
>


Visually indeed, the 2-axis rotation looks more "natural" than the 
3-axis rotation. However, I wonder if it is correct and my hunch would 
be that in RL rotation would imply 3-axis rotation nonetheless. This 
/must/ have been investigated somewhere, mustn't it?

-- 
Thomas

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