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Model with the mouse. Control it with code.

Every sketch, extrude and fillet you make with the mouse is written as a line of JavaScript. Change the code and the part rebuilds; change the part and the code follows.

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From a sketch to a solid

Build a rocker arm, one feature at a time. Every sketch, extrusion, cut and fillet has its own place in the history, and its own lines in the file.

Rocker armFeature 1 of 7

Fully constrain the arm profile with tangent semicircular ends, a 24 mm radius and pivot centers 76 mm apart.

rocker.part.js JavaScript
import {
  arc, circle, cut, extrude, fillet,
  line, origin, select, sketch,
} from "fluidcad/core";
import {
  coincident, diameter, distance,
  horizontal, radius, tangent,
} from "fluidcad/constraints";
import { edge } from "fluidcad/filters";
const SPAN = 76;
const ARM_RADIUS = 24;
const ARM_THICKNESS = 12;
const HUB_DIAMETER = 32;
const HUB_HEIGHT = 14;
const PIVOT_DIAMETER = 20;
const TIP_HOLE_DIAMETER = 11;
const FILLET_RADIUS = 4;


sketch("xy", () => {
  const bottom = line([0, -ARM_RADIUS], [SPAN, -ARM_RADIUS]);
  const tip = arc([SPAN, -ARM_RADIUS], [SPAN, ARM_RADIUS], [SPAN, 0]);
  const top = line([SPAN, ARM_RADIUS], [0, ARM_RADIUS]);
  const pivot = arc([0, ARM_RADIUS], [0, -ARM_RADIUS], [0, 0]);
  coincident(bottom.end(), tip.start());
  coincident(tip.end(), top.start());
  coincident(top.end(), pivot.start());
  coincident(pivot.end(), bottom.start());
  tangent(bottom, tip);
  tangent(tip, top);
  tangent(top, pivot);
  tangent(pivot, bottom);
  horizontal(bottom);
  horizontal(top);
  coincident(pivot.center(), origin());
  radius(pivot, ARM_RADIUS);
  distance(pivot.center(), tip.center(), SPAN, "x");
});

Choose a feature to see that point in the build. Its lines are highlighted in the file. Drag the model to explore it in 3D.

Assemble parts. Define how they move.

Insert reusable parts, fix one in place, and join their connectors with mates. Keep a connection rigid, let a hinge rotate, or guide a part along a slide. The assembly solver keeps the connections together.

const fixed = insert(fixedLeaf).grounded();
const moving = insert(movingLeaf);
const pin = insert(hingePin);


mate("revolute",
  fixed.connectors.pivot,
  moving.connectors.pivot,
).flip().limits(0, 180).name("hinge-swing");


mate("fastened",
  fixed.connectors.pivot,
  pin.connectors.axis,
).flip();

Explore assemblies →

Two leaves + a pin · press play to open · drag to orbit

Download

Desktop appv0.0.50

Other installation options

Install with npm0.0.50

$ npm i fluidcad
$ npx fluidcad init
$ npx fluidcad serve

Installed per project, so the engine and your editor’s type hints resolve from the same node_modules as the model.

Read the getting started guideBrowse the source

A browser version that needs no install is in progress. Today the engine already runs client-side in the viewer above.

Your agent, in the same workspace

Connect an AI agent through MCP. It can read and edit your model, inspect geometry, measure a face, and check its work with screenshots. You keep the source and see the changes in your viewport.

npx fluidcad mcp
Connect an agent →

Built with it

Every one of these is a tutorial: the drawing it came from, the sketch that starts it, and every statement in between.

All tutorials

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