Gaitkit Open the lab
Ballista, A torsion bolt thrower about 3 m long aiming toward +Z, on a tripod, a two-wheeled cart or a stone plinth for castle walls. The mount turns on y (traverse), the cradle tilts on x (elevation) and the windlass at the back spins; userData.tick sweeps it left and right while winding the windlass once per loop.
Prop · 3 moving parts

Ballista

A torsion bolt thrower about 3 m long aiming toward +Z, on a tripod, a two-wheeled cart or a stone plinth for castle walls. The mount turns on y (traverse), the cradle tilts on x (elevation) and the windlass at the back spins; userData.tick sweeps it left and right while winding the windlass once per loop.

Size
2.7 × 2.2 × 2.8 m
Triangles
820
Open in the lab Ready for any engine. The download carries the knobs you set here.

Tune it

4 knobs: Wood, Mount, Bolt, Size.

Specs

Size
2.7 × 2.2 × 2.8 m
width × height × depth
Triangles
820
of 6,000
Draw calls
1
one vertex-colour material
Loop clip
1 m
of travel per cycle
Moving parts
3
mount · rotate, cradle · rotate, winch · spin
Knobs
4
3 presets
Night lights
0
none

Passed the validator: real scale, rests on y = 0, front faces +Z, deterministic.

Use it

Code for the specimen as it is set up above; it follows your knobs.

JavaScript
import { createAsset } from 'https://gaitkit.com/cdn/ballista.mjs';

const ballista = createAsset();
scene.add(ballista);                      // rests on y = 0, front faces +Z

// 'mount' pivots on its hinge: -40° to 40° around y
ballista.getObjectByName('mount').rotation.y = THREE.MathUtils.degToRad(-40);

More in the docs; agents can fetch all of this through MCP.

Knobs

KnobTypeValuesDefaultWhat it does
woodchoiceoak pine weathered darkoakTimber tone: oak (warm brown), pine (light, freshly built), weathered (silver-grey), dark (tarred).
mountchoicetripod cart plinthtripodtripod (three splayed legs round a pivot post, field use), cart (two wheels and a trail, can be towed), plinth (a squat stone base for a castle wall walk or tower top).
bolttoggleon / offtrueA loaded 1.8 m iron-tipped bolt in the slide. Off shows it unloaded.
sizerange0.8 to 1.6, step 0.051Overall scale. 1 is about 3 m long and 2.6 m across the bow arms; 1.6 a heavy fortress engine.

Presets: wall scorpion {"mount":"plinth","wood":"dark"} · field ballista {"mount":"cart","wood":"pine"} · fortress engine {"mount":"plinth","size":1.5,"wood":"weathered"}

Files

FileWhat
ballista.glbGLB, default look · 120 KB
ballista.mjsES module, every knob live
ballista.objOBJ, static, no colour
ballista-params.jsonknob schema, presets, night zones

Licence

Use it in games, apps, renders and client work, commercially and without credit. Do not resell it as an asset or train a 3D generator on it. The full licence.

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