STEP Converter

Table of Contents

• Overview
• Scope
• Mapping
  • Import Mapping
    • Product Structure
    • Topology
    • Geometry
    • Polygonal
• Parameters
  • Importer Parameters
  • Exporter Parameters

Overview

STEP_Reader can read and STEP_Writer can write files compliant with STEP AP214 or AP242.

Scope

Import	Export
B-Rep representations polygonal representations assembly structure, including via external files names user-defined and validation properties PMI colors layers	B-Rep representations polygonal representations assembly structure, including via external files names user-defined and validation properties PMI colors layers

Mapping

Import Mapping

Below tables shows how STEP entities are mapped into CAD Exchanger entities after import.

Product Structure

STEP Entity	CAD Exchanger Entity	Note
product_definition	One of: ModelData_Assembly ModelData_Part
next_assembly_usage_occurrence	ModelData_Instance
item_defined_transformation	ModelData_Transformation
advanced_brep_shape_representation	ModelData_BRepRepresentation
faceted_brep_shape_representation	ModelData_PolyRepresentation	Supported only in version 2 of reader

Topology

STEP Entity	CAD Exchanger Entity	Note
manifold_solid_brep	ModelData_Body with type equal to ModelData_BT_Solid
brep_with_voids		Each void is mapped to inner ModelData_Shell
shell_based_surface_model	ModelData_Body with type equal to ModelData_BT_Sheet
face_based_surface_model
edge_based_wireframe_model	ModelData_Body with type equal to ModelData_BT_Wireframe
geometric_curve_set
geometric_set	ModelData_BodyList	Geometric entities are grouped by type (surfaces with surfaces, curves with curves, etc.) and form a list of homogeneous bodies (e.g., one sheet body and one wireframe body)
closed_shell	ModelData_Shell
oriented_closed_shell
open_shell
advanced_face	ModelData_Face
face_surface
curve_bounded_surface
face_bound	ModelData_Wire
face_outer_bound
edge_loop
connected_edge_set
composite_curve		Each segment is mapped to ModelData_Edge.
boundary_curve
outer_boundary_curve
edge_curve	ModelData_Edge
oriented_edge
vertex_point	ModelData_Vertex

Geometry

STEP Entity	CAD Exchanger Entity
Surfaces
b_spline_surface_with_knots	ModelData_BSplineSurface
rational_b_spline_surface
uniform_curve
quasi_uniform_curve
conical_surface	ModelData_ConicalSurface
cylindrical_surface	ModelData_CylindricalSurface
offset_surface	ModelData_OffsetSurface
plane	ModelData_Plane
rectangular_trimmed_surface	ModelData_RectangularTrimmedSurface
spherical_surface	ModelData_SphericalSurface
surface_of_linear_extrusion	ModelData_SurfaceOfLinearExtrusion
surface_of_revolution	ModelData_SurfaceOfRevolution
toroidal_surface	ModelData_ToroidalSurface
Curves
b_spline_curve_with_knots	ModelData_BSplineCurve ModelData_BSplineCurve2d
rational_b_spline_curve
uniform_curve
quasi_uniform_curve
circle	ModelData_Circle ModelData_Circle2d
ellipse	ModelData_Ellipse ModelData_Ellipse2d
hyperbola	ModelData_Hyperbola ModelData_Hyperbola2d
line	ModelData_Line ModelData_Line2d
offset_curve	ModelData_OffsetCurve ModelData_OffsetCurve2d
parabola	ModelData_Parabola ModelData_Parabola2d
trimmed_curve	ModelData_TrimmedCurve ModelData_TrimmedCurve2d

Polygonal

STEP Entity	CAD Exchanger Entity
faceted_brep	ModelData_IndexedTriangleSet

Parameters

Importer Parameters

Import parameters are controlled by STEP_ReaderParameters.

Parameter	Default value	Description
PreferredBRepRepresentationType()	Auto	Specifies the preferred B-Rep shape representation type, which should be imported. Auto - the most appropriate representation is chosen automatically. All - all representations are imported. This includes the main representation and all connected to it via relationships. AdvancedBRep - prefer ADVANCED_BREP_SHAPE_REPRESENTATION, which stores solid bodies. ManifoldSurface - prefer MANIFOLD_SURFACE_SHAPE_REPRESENTATION, which stores sheet bodies with shells. NonManifoldSurface - prefer NON_MANIFOLD_SURFACE_SHAPE_REPRESENTATION, which stores sheet bodies with faces. EdgeBasedWireframe - prefer EDGE_BASED_WIREFRAME_SHAPE_REPRESENTATION, which stores wireframe bodies. In case the preferred representation cannot be found, the first appropriate is imported.
ReadPMI()	false	See Base_ReaderParameters::ReadPMI().

Exporter Parameters

Export parameters are controlled by STEP_WriterParameters.

Parameter	Default value	Description
WriteBRepRepresentation()	true	See Base_WriterParameters::WriteBRepRepresentation().
WritePolyRepresentation()	false	See Base_WriterParameters::WritePolyRepresentation(). If more than one polygonal representations is present in model, which of them should be written is controlled by PreferredLOD(). Note If some part(s) in the model contain only polygonal representations (e.g., loaded from STL file), they will be converted regardless of this parameter.
PreferredLOD()	ModelData_RM_Medium	See Base_WriterParameters::PreferredLOD(). If combination of flags is used (i.e. ModelData_RM_Poly), then all respective representations are written.
LengthUnit()	Base_LU_Millimeters	See Base_WriterParameters::LengthUnit().
Author()	"Unspecified"	See Base_WriterParameters::Author().
Organization()	"Unspecified"	See Base_WriterParameters::Organization().
OriginatingSystem()	"Unspecified"	See Base_WriterParameters::OriginatingSystem().
PreferredBRepRepresentationType()	Auto	Specifies, which BRep shape representation type is preferred. Auto - representation type is chosen based on the type of bodies. AdvancedBRep - prefer advanced_brep_shape_representation, where bodies type is manifold_solid_brep ManifoldSurface - prefer manifold_surface_shape_representation, where bodies type is shell_based_surface_model NonManifoldSurface - prefer non_manifold_surface_shape_representation, where bodies type is face_based_surface_model EdgeBasedWireframe - prefer edge_based_wireframe_shape_representation, where bodies type is edge_based_wireframe_model If chosen representation type is not suitable for particular body, the best appropriate is used automatically.
ExternalReferencesMode()	Monolithic	Specifies whether external references sould be used to create resulting STEP file. Monolithic - no external references, single file with the whole model created. PerPart - every part is written to it's own STEP file; product structure is stored in single "master" file. PerAssembly - assemblies and parts are written to their own STEP files; "master" file contains only roots of product structure.
WritePCurves()	false	Specifies whether p-curves (edge curves in 2D parametric surface space) should be written. Writing p-curves can be helpful for certain receiving CAD systems to import data from STEP files. However writing p-curves can considerably increase an output file size.
WritePMI()	false	See Base_WriterParameters::WritePMI().
SchemaVersion()	AP242	Specifies the version of STEP file. AP214 AP242