import_step / export_step

The STEP I/O tools handle import and export of STEP AP203/AP214 files, the standard CAD interchange format. Import reads a STEP file from disk and produces an IR document with ImportedMesh nodes. Export (via the CLI) writes exact BRep geometry to STEP AP214 format.

import_step

Reads a STEP file and returns an IR document containing the imported geometry as ImportedMesh nodes.

Input Schema

Return Value

The tool returns a JSON response containing the IR document and an import summary:

{
  "document": {
    "version": "0.1",
    "nodes": {
      "1": {
        "id": 1,
        "name": "Housing",
        "op": {
          "type": "ImportedMesh",
          "positions": [...],
          "indices": [...],
          "normals": [...],
          "source": "housing.step"
        }
      }
    },
    "materials": {
      "steel": { "name": "Steel", "color": [0.6, 0.6, 0.65], "metallic": 0.9, "roughness": 0.3, "density": 7850 }
    },
    "roots": [{ "root": 1, "material": "steel" }]
  },
  "summary": {
    "bodies": 1,
    "total_triangles": 4582,
    "total_vertices": 2346
  }
}

ImportedMesh Nodes

Each body in the STEP file becomes an ImportedMesh node in the IR document. The node contains the tessellated triangle mesh (positions, indices, and optionally normals) plus a source field referencing the original filename. The tessellation is performed by the BRep kernel during import at a quality level appropriate for visualization and inspection.

The imported document can be passed to inspect_cad for volume and area measurement, to export_cad for format conversion (STEP to STL or GLB), or to open_in_browser for visualization.

Supported STEP Flavors

The importer handles STEP files produced by common CAD tools:

Combining Imported Geometry

After importing, you can combine imported geometry with new geometry by creating a document that references both. Use create_cad_document to build new parts and booleans, then merge the results.

Error Handling

The tool throws errors for:

• File not found: The specified path does not exist
• No geometry: The STEP file parses successfully but contains no solid bodies
• Parse failure: The STEP file is malformed or uses unsupported entities

export_step (CLI)

STEP export is available through the CLI rather than the MCP server. It writes exact BRep geometry to STEP AP214 format, preserving analytical surface types (plane, cylinder, cone, sphere, torus) without tessellation.

vcad export model.vcad model.step

Supported Geometry

Bilinear planar surfaces export as PLANE entities. Non-planar degree-1 surfaces export as B_SPLINE_SURFACE_WITH_KNOTS. Control point coordinates use full f64 precision ({:.15E} format) to prevent loss during round-trip.

Round-Trip Fidelity

For documents containing only primitives and imported STEP geometry (no booleans), the STEP export preserves exact geometry. Importing the exported file produces identical surfaces within floating-point precision. This makes vcad suitable as a STEP format converter or viewer.

For the import/export workflow tutorial, see STEP Import.