> ## 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.

# STEP export (experimental)

> Export B-Reps and scenes to STEP (Part 21) text

<Warning>
  STEP export is experimental and may change. If you hit an exporter limitation or confusing output,
  reach out on [Discord](https://discord.gg/cZY2Vm6E).
</Warning>

## Overview

OpenGeometry can export B-Reps to **STEP Part 21** text. You can export a single B-Rep payload or
export a whole scene through `OGSceneManager`.

## 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

### exportBrepToStep

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

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

### exportSceneToStep / exportCurrentSceneToStep

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

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

const result = manager.exportSceneToStep(sceneId);
// or:
const result2 = manager.exportCurrentSceneToStep();
```

## Result type

`export*ToStep(...)` returns an `OGStepExportResult`:

<ResponseField name="text" type="string">
  STEP Part 21 text output.
</ResponseField>

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

## Config JSON

All STEP 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
`StepExportConfig` shape (required fields must be present).

Default configuration (Rust):

```rust theme={null}
StepExportConfig {
  schema: StepSchema::AutomotiveDesign,
  product_name: Some("OpenGeometry STEP Export".to_string()),
  scale: 1.0,
  error_policy: StepErrorPolicy::BestEffort,
  validate_topology: true,
  require_closed_shell: true,
}
```

Example JSON payload:

```json theme={null}
{
  "schema": "AutomotiveDesign",
  "product_name": "OpenGeometry STEP Export",
  "scale": 1.0,
  "error_policy": "BestEffort",
  "validate_topology": true,
  "require_closed_shell": true
}
```

## Key constraints

* When `require_closed_shell` is `true`, non-solid inputs are skipped in best-effort mode.
* When `validate_topology` is `true`, invalid B-Reps are skipped (or fail in strict mode).

## Examples

### Export and download STEP in the browser

```ts theme={null}
const result = manager.exportCurrentSceneToStep();

const blob = new Blob([result.text], { type: "text/plain" });
const url = URL.createObjectURL(blob);

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

URL.revokeObjectURL(url);
```

### Native-only file export

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

## Related

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