Times Square Ball Drop: Descent Mechanics (3D)

Spool Servo

Controller gain (aggressiveness) 1.0

Wind-gust disturbance 30%

Cable friction variation 25%

Cable stiffness Medium

Click the ball or the button to arm a 5‑second countdown. Orbit with drag, zoom with scroll/pinch.

Descent Readout

Spool position

60.0 ft

Ball height

60.0 ft

Cable stretch

0.00 ft

Tension

1.00 × mg

How it works

Here the motor doesn't drive the ball's height directly — it drives a spool whose commanded position follows the ideal 60‑second linear schedule, corrected by a proportional feedback loop comparing the spool's own commanded position against the ball's sensed actual height (spool_v = target_v + Kp·(spool_y − ball_y)). The cable connecting spool to ball is modeled as a stiff spring plus damper, not a rigid rod: the ball's true motion obeys m·ÿ = m·g − k·(y_ball − y_spool) − c·ẏ_ball, so the ball can lag or overshoot the spool briefly — real cable elasticity — while gravity is almost, but not exactly, cancelled by cable tension throughout the descent.

Wind is applied as a genuine lateral force, swinging the ball sideways on the cable (a pendulum-like sway) rather than only perturbing the vertical rate, and cable friction randomly resists the spool's payout. This is a second-order, spatial rendering of the same real control problem as the 2D companion sim, but built from different state (spool position + elastic cable + 3D sway) rather than a flattened copy of it.

Controller gain — spool servo aggressiveness correcting for ball-vs-schedule error.
Wind-gust disturbance — a lateral aerodynamic force that swings the ball off-axis.
Cable friction variation — randomly resists spool payout, decoupling spool speed from commanded speed.
Cable stiffness — how rigid the cable is: low stiffness shows visible stretch/bounce, high stiffness approaches a rigid link.

t = 0.0 s · h = 60.0 ft

⚠ Couldn't load the 3D engineThree.js failed to load from the CDN. Check your connection and reload.