Measure
Recover motion and geometry
Video, IMUs, force insoles, LiDAR, wind, and hill geometry become time-indexed evidence for the digital twin.
World Models / Sports dynamics / Trajectory optimization
Ski Jumper Digital Twin
From motion capture to physics-aware simulation, the model optimizes a full body-and-ski trajectory rather than a single pose.
Based on the July 2026 Ski Jumper / Human Digital Twin report. This page presents the proposed model contract and claim boundary for future simulation work.
Optimize the trajectory, not one pose
A jump is a schedule through changing physics.
The same body has different objectives on the in-run, at takeoff, in early flight, during stable flight, before landing, and at contact. The twin makes the hill, skeleton, skis, forces, and phase label explicit so those objectives can be simulated and optimized together.
Model
Expose the model contract
State, parameters, inputs, constraints, kinematics, and dynamics define what the simulator can answer and what it cannot.
Simulate
Bridge motion to forces
Forward kinematics produce velocities, accelerations, center-of-mass paths, contact loads, and aerodynamic moments.
Optimize
Balance distance and safety
The objective trades landing distance against impact, instability, rule violations, excessive effort, and unrealistic motion.
Visual map
A visual contract for the jump
These views keep the project grounded: a full pipeline, a phase schedule, and a concrete contract for the state and dynamics.
Workflow
Six phases, six mechanical priorities
A world model becomes useful when the changing objective is visible across time. Each phase contributes a distinct constraint or target to the trajectory.
In-run
Preserve speed while reducing drag and maintaining track stability.
Takeoff
Create release velocity and angular momentum through contact impulse.
Early flight
Reach a stable V-style posture while controlling pitch, roll, and yaw.
Stable flight
Balance lift, drag, ski incidence, and aerodynamic efficiency.
Landing prep
Prepare ski attitude, center of mass, and leg posture for contact.
Landing
Absorb impact while preserving alignment, style, and safety.
Technical view
From pose to physics without overclaiming
The report treats a static figure as the beginning of an inspectable object. Each stronger physical claim requires a stronger evidence layer and an explicit dynamics model.
State and geometry
The state includes root pose, joint angles and rates, center-of-mass position and velocity, ski orientations, and a phase label. Parameters include segment masses, inertias, equipment, hill shape, wind, and friction.
Kinematics to dynamics
Forward kinematics produce segment positions and Jacobian velocities. Adding mass, inertia, gravity, contact, and aerodynamic loads yields a bridge to inverse dynamics.
- Position -> velocity -> acceleration
- Center-of-mass trajectory stays queryable
- Contact and aero loads remain separate inputs
Recoverability boundary
Static geometry supports visual pose. Time-indexed motion supports animation and kinematics. Forces and performance require inertias, contact and aero models, and validation data.
- Visualized: geometry, pose, and phase
- Computed: kinematics, COM, and trajectories
- Estimated or validated: forces, impact, and performance
Current scope
A world model for a changing body and environment
The project turns ski jumping into a queryable simulation problem: expose the hill, skeleton, equipment, forces, and phase transitions, then optimize a physically meaningful trajectory under safety and rule constraints.