Importing a CAD file

ShapeLoader loads STEP / IGES / BREP / STL / OBJ / JWW into OCCT Shapes plus document metadata, with no Viewport dependency. The entry points are async throws static methods on the ShapeLoader enum; both return a ShapeLoadResult.

Pick the format

A CADFileFormat selects the per-format code path. You can hard-code it, or detect it from the file extension:

import OCCTSwift
import OCCTSwiftIO

guard let format = CADFileFormat(fileExtension: url.pathExtension) else {
    throw CocoaError(.fileReadUnsupportedScheme)   // unrecognised extension
}
let result = try await ShapeLoader.load(from: url, format: format)

CADFileFormat(fileExtension:) accepts step/stp, stl, obj, brep/brp, iges/igs, and jww (case-insensitive), returning nil for anything else.

Read shapes, colors, and AP242 metadata

let result = try await ShapeLoader.load(from: stepURL, format: .step)

// Shapes paired with their per-shape color (nil for formats that carry none).
for (shape, color) in result.shapesWithColors {
    print(shape, color as Any)
}

// Or just the shapes, dropping color info:
let shapes = result.shapes

// AP242 GD&T (STEP only; empty otherwise):
print(result.dimensions, result.geomTolerances, result.datums)

STEP carries per-shape colors and AP242 dimensions / tolerances / datums; STL, OBJ, BREP, and IGES return shapes with nil colors and empty metadata arrays.

Robust loading for messy files

STL and IGES files frequently ship with gaps OCCT’s basic importer can’t close. loadRobust routes those two formats through the sewing/healing path (for STEP / OBJ / BREP it is identical to load):

let healed = try await ShapeLoader.loadRobust(from: igesURL, format: .iges)

JWW (2D vector drawings)

JWW is a Jw_cad 2D drawing — not a solid or a mesh. It loads to a single compound Shape of OCCT edges in the Z = 0 plane (lines, circular arcs, ellipse polylines, and points):

let drawing = try await ShapeLoader.load(from: jwwURL, format: .jww)
let compound = drawing.shapes.first   // one compound of edges/vertices