> ## Documentation Index
> Fetch the complete documentation index at: https://docs.opengeometry.io/llms.txt
> Use this file to discover all available pages before exploring further.

# STL export (experimental)

> Export B-Reps and scenes to binary STL

## Overview

OpenGeometry can export B-Reps to **binary STL**. You can export a single B-Rep payload or export a
whole scene through `OGSceneManager`.

<Warning>
  STL export is experimental. Output, config fields, and file-writing helpers may change. If you hit
  an exporter limitation or confusing output, reach out on
  [Discord](https://discord.gg/cZY2Vm6E).
</Warning>

<Note>
  The WebAssembly build returns STL as bytes (`Uint8Array`). You are responsible for downloading or
  persisting those bytes. Some file-writing convenience methods exist only in native builds.
</Note>

## Initialization

Initialize the WASM module once before using `OGSceneManager`:

```ts theme={null}
import { OpenGeometry } from "opengeometry";

await OpenGeometry.create({ wasmURL: "/opengeometry_bg.wasm" });
```

## Export APIs

### exportBrepToStl

Export a single serialized B-Rep JSON string to STL bytes.

```ts theme={null}
import { OGSceneManager } from "opengeometry";

const manager = new OGSceneManager();
const result = manager.exportBrepToStl(brepSerialized);
```

### exportSceneToStl / exportCurrentSceneToStl

Export a stored scene (or the current scene) to STL bytes.

```ts theme={null}
import { OGSceneManager } from "opengeometry";

const manager = new OGSceneManager();
const sceneId = manager.createScene("stl export");

// Add entities to the scene, then:
const result = manager.exportSceneToStl(sceneId);
// or:
const result2 = manager.exportCurrentSceneToStl();
```

## Result type

`export*ToStl(...)` returns an `OGStlExportResult`:

<ResponseField name="bytes" type="Uint8Array">
  The binary STL bytes.
</ResponseField>

<ResponseField name="reportJson" type="string">
  A JSON string containing export statistics (triangle counts, skipped faces, topology errors).
</ResponseField>

## Config JSON

All STL exports accept an optional `config_json` string. If it is `null`, `undefined`, or an empty
string, OpenGeometry uses defaults. If you provide `config_json`, it must deserialize into the full
`StlExportConfig` shape.

Default configuration (Rust):

```rust theme={null}
StlExportConfig {
  header: Some("OpenGeometry STL Export".to_string()),
  scale: 1.0,
  error_policy: StlErrorPolicy::BestEffort,
  validate_topology: true,
}
```

Example JSON payload:

```json theme={null}
{
  "header": "My STL export",
  "scale": 1.0,
  "error_policy": "BestEffort",
  "validate_topology": true
}
```

## Examples

### Export a wrapper shape to STL

`OGSceneManager` expects a serialized B-Rep string. Wrapper shapes expose one of `getBrep()`,
`getBrepData()`, or `getBrepSerialized()` depending on the type.

```ts theme={null}
import { Cuboid, OGSceneManager, Vector3 } from "opengeometry";

function toBrepSerialized(source: unknown) {
  const value =
    source && typeof (source as any).getBrepSerialized === "function"
      ? (source as any).getBrepSerialized()
      : source && typeof (source as any).getBrepData === "function"
        ? (source as any).getBrepData()
        : source && typeof (source as any).getBrep === "function"
          ? (source as any).getBrep()
          : source;

  return typeof value === "string" ? value : JSON.stringify(value);
}

const manager = new OGSceneManager();
const sceneId = manager.createScene("export");

const cuboid = new Cuboid({
  center: new Vector3(0, 0.5, 0),
  width: 2,
  height: 1,
  depth: 1,
  color: 0x10b981,
});

manager.addBrepEntityToScene(
  sceneId,
  "box-1",
  "Cuboid",
  toBrepSerialized(cuboid)
);

const result = manager.exportSceneToStl(sceneId);
console.log(JSON.parse(result.reportJson));
```

### Download STL in the browser

```ts theme={null}
const blob = new Blob([result.bytes], { type: "application/octet-stream" });
const url = URL.createObjectURL(blob);

const link = document.createElement("a");
link.href = url;
link.download = "model.stl";
link.click();

URL.revokeObjectURL(url);
```

### Write STL in Node.js

```ts theme={null}
import { writeFileSync } from "node:fs";

writeFileSync("model.stl", Buffer.from(result.bytes));
```

### Native-only file export

<Note>
  Native-only builds also expose `exportSceneToStlFile(...)` (not available in browser/WASM builds).
</Note>

## Related

* [Exports](/OpenGeometry/concepts/exports) for an overview of available exporters and runtime constraints
* [STEP export](/OpenGeometry/api/export/step) (experimental)
* [IFC export](/OpenGeometry/api/export/ifc) (experimental)