[resource] quaternion calculator and euler angle translator

[dmarx]

https://quaternions.online/

[dmarx]

https://discord.com/channels/869630568818696202/869675528494391307/911779334312837161

Я — 11/20/2021
To rotate about an axis [x, y, z] by a degrees you will need

rotate_3d: [cos(radians(a/2)),x*sin(radians(a/2)),y*sin(radians(a/2)),z*sin(radians(a/2))].

For example to rotate by 3 degrees per frame about:

• The x axis (looking up and down): rotate_3d: [cos(radians(3/2)),sin(radians(3/2)),0,0]
• The y axis (looking left and right): rotate_3d: [cos(radians(3/2)),0,sin(radians(3/2)),0]
• The z axis (tilting your head side to side): rotate_3d: [cos(radians(3/2)),0,0,sin(radians(3/2))]

since cos(0) = 1 and sin(0) = 0, to rotate by 0 degrees (i.e. to not rotate) just do

rotate_3d: [1,0,0,0]

[dmarx]

you need to understand how much you want to rotate each frame and also what axis you want to rotate around
representing the axis as a unit vector x,y,z
the rotation is rotate_3d: [cos(a),x*sin(a),y*sin(a),z*sin(a)]
where a is the rotation angle in radians
so to very that with time you make a a function of t

-- https://discord.com/channels/869630568818696202/869675528494391307/924046784408453150

[dmarx]

<blockquote class="twitter-tweet"><p lang="en" dir="ltr"><a href="https://t.co/7y7B0XyTKm">https://t.co/7y7B0XyTKm</a><br><br>rotate_3d: [cos(radians(6)),0,-sin(radians(6))/sqrt(2),sin(radians(6))/sqrt(2)]<br><br>translate_x: -1700*sin(radians(6)) <a href="https://t.co/BCQTYkRRjz">pic.twitter.com/BCQTYkRRjz</a></p>&mdash; ya (@sportsracer48) <a href="https://twitter.com/sportsracer48/status/1451562757174743047?ref_src=twsrc%5Etfw">October 22, 2021</a></blockquote> <script async src="https://platform.twitter.com/widgets.js" charset="utf-8"></script>

[dmarx]

Alternatively, the R_is_Ris vesrion

[cos(pi/a),cos(pi/(a*b)),d*cos(pi/(a*c)),cos(pi/a)], where abcd are constants that suit the motion of the scene (higher value, slower rotation)

[dmarx]

this isn't a docs thing, but this feels like the right place to put it for now: https://github.com/moble/quaternion

[dmarx]

https://thenumb.at/Exponential-Rotations/