POV-Ray : Newsgroups : povray.general : Rotation around an axis at the origin : Re: Rotation around an axis at the origin Server Time
7 Aug 2024 19:22:04 EDT (-0400)
  Re: Rotation around an axis at the origin  
From: Jérôme Grimbert
Date: 17 Jul 2001 17:12:25
Message: <3B54A98A.D77B3945@free.fr>
Greg Smith wrote:
> 
> Hey, I suggested this as a new feature a few years back.
> 
> rotate_unform <rot_vector>
>    -or-
> rotate_uniform angle*<normal>
> 
> rotates about the given vector, by an angle equal to the magnitude
> of the vector.
> 
> The usefulness of this is that rotations interpolate much better
> in this space. If you have an animation and you describe rotations
> at keyframes by this means, interpolations between the keyframes
> based on interpolations in the rotation vector space work much better
> since the space is uniform (except for rotation close to 180 degrees).
> With the standard rotation, you can get weird effects if the interpolation
> path happens to come close to the 'north pole' if you see what I mean.
> 
> I see other have helped you with this already....

rotate_uniform would not have solved my purpose, because
the angle is different for each point of the original object
(for screwing, it is proportional to the projection on the axis,
for rolling, it is proportional to the distance to the axis), so
I really needed the formulae (I compute a full matrix for each point now !)

May I suggest, nevertheless, that you find a more 'simpler' term,
if you expect this extension to enter any release.
I would suggest something like 'turn' 
(as 'turn' around <x,y,z> axis, like 'rotate' by <x,y,z> degres )
Or try any single word which may be a synonym for 'rotate'.


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