Where a vehicle's tyres touch the ground: one entry per wheel, fleet-local position at ground
level, an influence radius (half the tyre's width plus a margin) and a strength (heavier
vehicles press harder; 1 for a tractor's rear wheels). Plain data, ready for grass or crop
interaction (threejs-grass bends blades within radius of an interactor's position).
Where a vehicle's tyres touch the ground: one entry per wheel, fleet-local position at ground level, an influence
radius(half the tyre's width plus a margin) and astrength(heavier vehicles press harder; 1 for a tractor's rear wheels). Plain data, ready for grass or crop interaction (threejs-grass bends blades withinradiusof an interactor's position).