Preparing the mechanics bench…
No instructions to follow. Just things to discover.
Pick a part. Make something happen.
This is an open workbench. Choose a part from the drawer, then click or tap the bench to place it. Grab a pendulum, upset a stack, or take gravity away.
Drag a body to grab it with a spring-like force. Drag empty space to orbit; right-drag to pan. Scroll or pinch to zoom. On touch, one finger orbits and two fingers pan and zoom.
Space pauses. F focuses a selection. H returns to the bench. Delete removes a selected body; Shift + Delete removes its assembly. Esc cancels placement.
Pause to position bodies precisely. The arrow buttons move by 10 cm; rotation turns by 15°. Reset rebuilds your chosen starting bench. Save and Load use this device’s browser storage. Connect spring joins a selected body to the next body you tap, using their current separation as the rest length. Unlink removes connections to a selected body. CSV exports up to 12 seconds of the current measurements.
Lengths are metres, masses kilograms and time simulation seconds. K is kinetic energy including rotation; U is gravitational potential measured from the tabletop (so it can be negative below it); S is the energy of a connected spring. Spring energy appears in full for either attached body; do not add both readings together.
Materials use representative bulk densities. Friction and restitution are adjustable presets, averaged between touching surfaces. Apparatus bobs and weights use explicit mass overrides, shown in the inspector.
Gravity changes, grabs, repositioning, pins and edits do external work. Restitution below 1, friction and spring damping dissipate energy. Total displayed energy is not conserved in those cases.
Rapier 0.20.0 rigid-body dynamics at a fixed 1/120 s timestep, 12 solver iterations and continuous collision detection for dynamic bodies. Up to 120 editable bodies and 12 catch-up steps per rendered frame. A stalled tab discards excess wall time; the simulation clock tracks only integrated time.
Pendulum rods are massless visual links with a spherical or revolute pivot. Bobs have rotational inertia. Springs apply Hooke’s law plus axial viscous damping; a vertical guide constrains the spring mass. Spring forces use symmetric half-step impulses around the rigid-body step; connected masses stay awake. Other settled bodies can sleep. Lever pivots are ideal hinges. The ramp is a solid inclined deck; small bolts, support trim and decorative rod meshes do not collide.
No air drag, deformation, fracture, fluids or calibrated contact materials. Finite-step contacts and constraints introduce numerical error. The cradle is an approximate rigid-body collision experiment, not an exact analytical Newton’s cradle. Rendering follows the latest integrated state, with no extrapolation.
Rapier: contacts and materials · Rapier: constraints