Each snowflake falls under gravity while wind adds a horizontal advection term proportional to wind speed, plus a small per-flake turbulence wobble. Visibility is modeled as a decreasing function of the airborne flake density crossing the line of sight and the wind speed (faster wind lofts more flakes and hides distant terrain): visibility ≈ 2000 / (1 + density/300 + wind/6) meters, clamped between 20 m (whiteout) and 2000 m (clear).
- Wind speed — tilts the fall trajectory, raises the visibility penalty, and drives horizontal transport of settled snow across the ground.
- Snow density — sets how many flakes are airborne at once, directly reducing visibility independent of wind.
- Drift accumulation — settled snow on the ground is redistributed downwind each step (like blown sand). The fence post blocks that transport, so snow piles up on its windward side into a real drift while the open ground stays a thin, even layer — the same lee-side pileup and windward scour you see next to real fences and snow fences.