Lucas Vieira (LucasVB) makes animated visualizations of mathematics and physics, many of them used on Wikipedia.
HN commenters call him a master of math visualization, praise his clear animations such as line integrals and Fourier series, and note his POV-Ray and PHP tooling.
From his tumblr: http://1ucasvb.tumblr.com/faq:
The 3D stuff (with shadows and such) was created using the excellent, free raytracer POV-Ray.
The rest were created using a custom-made PHP library that uses GD for graphics. The library adds a whole lot of functionality that isn’t present in GD or PHP: drawing anything with alpha blending, geometry and math primitives, 2D and 3D rotations (including quaternions), better anti-aliasing, object-oriented interface, etc.
The first time I was able to properly visualize sine and cosine was from an old 8mm film reel produced in the 1950s by IBM which showed essentially this same animation:
http://1ucasvb.tumblr.com/post/43524004530/drawing-process-for-the-sine-function-since
After seeing that, trig really just "clicked".
LucasVB is another master of visualizing mathematics. He is responsible for some of the best math animations on Wikipedia.[1] If you like to know more about how he creates these masterpieces, check out his Blog.[2]
[1] https://en.wikipedia.org/wiki/User:LucasVB/Gallery
[2] http://1ucasvb.tumblr.com/
This is by LucasVB, who is prolific at animating math for Wikipedia:
https://en.wikipedia.org/wiki/User:LucasVB/Gallery
His other works are also worth checking: http://1ucasvb.tumblr.com/
(for example, he has a super-nice explanation of Fourier series).
Interesting to note that the author, LucasVB, uses a custom PHP library using GD to make these animations. He explains why he finds alternatives like Processing, Matplotlib, etc. insufficient here:
http://1ucasvb.tumblr.com/faq
I like how this conveys the 3-dimensionality, in contrast to most othe visualizations. Also have a look at the animated version:
http://1ucasvb.tumblr.com/post/142549026838/figured-id-add-a-mass-in-there-see-also#_=_