Cross-Country Ski Glide Physics (3D)

The 2D original was a placeholder — a static description panel with no interactive canvas. This 3D companion replaces it with an actual cross-country skiing physics model. The skier moves along a real hill profile built from sine harmonics, and every physics step sums the genuine forces acting along the slope: gravity resolved along the slope tangent (−mg·sinθ), glide friction between ski base and snow (set by a wax-quality slider, μ from 0.02 to 0.10), aerodynamic drag that depends on which technique you pick, and a propulsive kick force scaled by both your effort slider and a metabolic fatigue reservoir that drains with power output and slowly regenerates when you ease off. Three techniques — classic diagonal stride, skate skiing and double poling — each carry their own peak force, drag area and metabolic efficiency, exactly as on real snow, so pacing choices actually change how the hills on the back half of the course play out.