This is a discrete granular-pile (angle-of-repose) model, viewed edge-on. A drop point sweeps back and forth above the pile — the 2D projection of the 3D version's orbiting drop point tracing a helix — releasing grains that fall ballistically (v' = v + g·dt) until they hit the current pile surface, where they settle and raise that column's height by a fixed grain increment.
After every deposit the whole height field is relaxed: for each pair of neighbouring columns spaced Δx apart, if the height difference exceeds Δx·tan(θc) — the real critical slope for the chosen angle of repose θc — sand is transferred downhill until every local slope is at or below that limit. This is the same toppling rule that governs real dry granular piles (θc ≈ 30–35° for dry sand) and is why the pile's measured flank angle converges on the slider's critical angle regardless of how fast or unevenly grains are dropped.
- Angle of repose — the maximum stable slope; raise it for a taller, steeper cone, lower it for a flat, spread-out pile.
- Grain settle size — how much height one grain adds; larger grains produce coarser, more visible avalanches.
- Orbit speed / radius — how the drop point sweeps, which controls whether the pile grows as one steep cone (slow/narrow orbit) or a wide double-ridged mound (fast/wide orbit) — the side-view trace of the helix path.