Engineering
Beam Vibration Mode (n=3)
w(x,t) = sin(3πx/L)·cos(ωt)

The third natural mode of a simply-supported beam: two interior nodes stay fixed while the antinodes swing up and down in step at the modal frequency.
Computed & rendered in pure C# on the frozen OnlyCSharp 1.8 library — animation baked to GIF with the library's own
Gif encoder (no GPU, no ffmpeg, no external packages).