Agriculture & Environmental
Fire Rate of Spread (Rothermel)
R = R0·(1+U)^1.5·(1+2·φs)

Wildfire spread accelerates nonlinearly with wind; sweeping the slope factor shows how a steeper hillside, which preheats fuel ahead of the front, multiplies the rate of spread on top of the wind effect.
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).