STEP-G(1)

NAME

step-g - import an ISO 10303 STEP file into a BRL-CAD geometry database

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SYNOPSIS
DESCRIPTION
OPTIONS
IMPORT POLICY
SCHEMA SELECTION
CONVERSION COVERAGE
METADATA AND PMI
DIAGNOSTICS
EXIT STATUS
EXAMPLES
SEE ALSO
AUTHOR
COPYRIGHT
BUG REPORTS

SYNOPSIS

step-g [options] input.step output.g
step-g [options] (-o output.g | -O output.g) input.step
step-g -D [options] input.step

step-g reads an ISO 10303-21 exchange file, selects a schema plugin from its FILE_SCHEMA header, and converts supported products and geometry to a BRL-CAD database. Builds with all STEP schemas enabled recognize AP203, AP203 edition 2, AP214 edition 3, and AP242 editions 1 through 4.

The default policy favors usable output from imperfect exchange files. It performs conservative repairs, may use bounded geometric inference after an ordinary conversion fails validation, and preserves a completed storage-safe invalid B-rep as a marked non-region when valid recovery is not possible. Usable partial output is published with status 1 and a diagnostic. Use the validation options below when repaired, inferred, invalid, or partial output is not acceptable.

Solids, surfaces, wireframes, tessellations, product structure, and selected metadata are converted when supported by the chosen application protocol. Native CSG in AP203e2, AP214, and AP242 is imported automatically. AP242 PMI is retained in a structured graph; resolvable datum and graphical annotation content also becomes native BRL-CAD objects. See STEP(5) for detailed representation and metadata coverage.

input.step may be -; standard input is spooled while its header is inspected. An existing output database is replaced only with -O or --force. Diagnostics go to standard error. After indexing, an entity census is printed to standard output before geometry conversion begins.

OPTIONS

General operation

-h, --help: Print usage and option information.
-o, --output output.g: Create output.g and refuse to overwrite an existing file.
-O, --output-overwrite output.g: Create output.g, replacing an existing file.
-f, --force: Permit the selected output file, including a positional output, to be overwritten.
-D, --dry-run: Parse, index, validate, and exercise conversion without writing a database. An output name is optional in this mode.
-v, --verbose: Report entity-level diagnostics.

Schema and content selection

--schema AP: Override AP242 edition selection with ap242e1, ap242e2, ap242e3, or ap242e4. The default auto mode tries compatible AP242 layouts from the newest to the oldest. For other AP families, an explicit value must agree with FILE_SCHEMA.
-e, --entity ID[,ID…]: Convert only the listed representation-item roots while retaining required product and assembly context. IDs are positive Part 21 instance identifiers with an optional # prefix. The option may be repeated.
--skip-open-shells: Exclude standalone OPEN_SHELL boundaries supplied by SHELL_BASED_SURFACE_MODEL items. Closed surface-model boundaries and the closed shells used by solid B-rep entities are unaffected.

Validation and repair policy

--repair MODE: Select safe or none. The default safe mode permits conservative topology and recognized data repairs. none also disables permissive modeling inference.
--exact: Enforce the model’s declared geometric tolerance instead of allowing the normal verified tolerance relaxation. Modeling inference is disabled.
--strict: Treat skipped, invalid, malformed, unsupported, or otherwise partial conversion as failure and do not publish a partial database. Invalid B-rep preservation and modeling inference are disabled.
--reject-invalid-objs: Reject invalid B-reps instead of preserving completed storage-safe objects as marked non-regions. This also disables modeling inference.
--abs-tol MM: Request an absolute output tolerance in millimetres. Zero uses the importer policy derived from the file and BRL-CAD defaults.

For AP242 tessellations, safe repair may reverse triangle winding to agree with supplied normals. --exact or --repair none rejects that mismatch.

Work control

-j, --jobs N: Set the number of geometry workers. The default is the available processor count, capped at eight.
--budget-scale FACTOR: Scale automatically calculated per-item conversion budgets.
--item-budget SECONDS: Set the per-item CPU-work budget explicitly.
--no-item-budget: Disable per-item CPU-work budgets.
--stall-timeout SECONDS: Set the no-progress timeout used to detect a stalled conversion.

Reports

--report FILE: Write a brlcad-step-import-report-v1 JSON report. It records schema and representation coverage, diagnostics, timing, repairs and inference, hierarchy semantics, material and product properties, retained configuration and AP242 PMI graphs, and the disposition of every product-bound representation item. The aggregate outcome is complete, partial, empty, or failed.
-S, --summary FILE: Write a per-instance CSV with output name, source identifier, entity type, and conversion status. The aggregate entity census is printed automatically and does not require this option.

IMPORT POLICY

The importer first builds source-faithful geometry and validates the complete result. Safe mode may then apply bounded repairs whose measured effect stays within the file and model tolerances. Repairs are recorded in diagnostics and the JSON report. --repair none disables them; --exact additionally prevents verified tolerance relaxation.

If explicitly associated curves contradict each other beyond the safe-repair limit but within a scale-bounded inference limit, default mode may retry the whole item with an inferred curve or pcurve. The retry is transactional: its geometry is accepted only when the rebuilt complete B-rep passes the ordinary structural and solidness validation. Accepted inference is tagged on the object and reported separately from safe repair. --exact, --strict, --repair none, and --reject-invalid-objs disable this path.

If no valid candidate can be built, default mode may retain a completed, storage-safe invalid B-rep for inspection rather than omit it. The object is not a region and carries step:geometry_status=invalid_preserved and step:source_validity=unresolved. These tags do not assert that the source file is wrong; the failure may still be an importer limitation. Missing or unsafe geometry is omitted as the final fallback.

SCHEMA SELECTION

The importer accepts one supported AP family in FILE_SCHEMA. A supported AP plus an unknown companion identifier is accepted with a warning; a sole unknown schema or multiple supported AP families is rejected. IFC headers are recognized and directed to the separate ifc-g(1) converter.

The AP242 long-form identifier does not state an edition. Automatic mode tries edition 4, 3, 2, and 1 physical layouts in that order when an attempted layout cannot produce usable geometry. A common subset can remain ambiguous, so use --schema ap242eN when the authoring edition is known.

The interim identifiers CONFIGURATION_CONTROL_3D_DESIGN_MIM_LF, CCD_CLA_GVP_AST, and CCD_CLA_GVP_AST_ASD select AP203e2. Verified multi-schema AP203 extension headers combining CONFIG_CONTROL_DESIGN with geometric-validation-property or shape-appearance-layer identifiers also use that binding. See STEP(5) for the compatibility and schema-source policy.

CONVERSION COVERAGE

The principal supported paths are:

advanced and faceted B-reps, B-reps with voids, open and closed surface models, mapped items, replicas, and rigid transformations;
bounded wireframes and geometric sets, with curves stored as B-reps, points as pnts, and reference planes as datum objects;
exact area and face extrusions and revolutions, plus supported linear and circular swept disks in AP203e2, AP214, and AP242;
AP242 triangulated faces, strips, fans, surface sets, shells, and solids as validated BOTs; and
supported native CSG expressions and primitives in AP203e2, AP214, and AP242.

Unsupported exact sweep subtypes and directrices are reported rather than approximated. A tessellated solid is marked solid only when its triangles form a closed, consistently oriented mesh; incomplete input remains a surface BOT.

AP203 assembly import recognizes the referenced/CDSR, mapped-shape, and replicated NAUO styles described by Recommended Practice 8. Multi-level assemblies, repeated rigid occurrences, and secondary representations are retained without confusing representation placement with product occurrence.

METADATA AND PMI

Stable product, revision, presentation, layer, material, property, unit, and occurrence values are stored as step: attributes on their owning BRL-CAD objects. Configuration-management and other reference-linked records without a direct object equivalent are retained in the versioned _STEP_METADATA binary object. _GLOBAL carries a locator and, for modest graphs, an editable compatibility copy. Source identifiers are internal anchors only; g-step allocates new Part 21 identifiers when it can legally re-author the records.

AP242 semantic and presentation PMI is retained in that graph and in the JSON report. Unambiguously resolved datum points, axes, and planes become native datum objects. Tessellated graphical curves reached through an annotation plane and draughting callout become model-space annot objects. Graphical outlines are not claimed to reconstruct semantic text, and unsupported PMI remains explicitly represented in the graph. PMI export is not yet supported.

DIAGNOSTICS

The pre-conversion census lists the total Part 21 instance count, every entity keyword used, and how many of those entity types are present in the selected schema. Complex instances contribute their explicit component types. The census describes file content, not conversion coverage.

The JSON report classifies each product-bound item as handled, preserved_invalid, filtered, intentionally_non_geometric, skipped, malformed, or unsupported, with its source identifier and reason. Explicitly filtered geometry does not make an otherwise complete import partial.

EXIT STATUS

Status 0 means complete validated geometry was published. Status 1 means usable partial geometry was published with all omissions and preserved invalid fallbacks reported. Status 6 means represented products contained only intentionally non-geometric items, or all geometry was explicitly filtered, and no database was published. Other nonzero statuses indicate input, conversion, strict-policy, or output failure; no partial database is published for those statuses.

EXAMPLES

Example 1. Import using automatic schema selection

step-g -o widget.g widget.step
mged widget.g 'tops'

Example 2. Validate strictly and write a JSON report

step-g -D --strict --report suspect.json suspect.step

Example 3. Inspect selected representation items without repair

step-g --repair none --entity '#410,#725' -o selected.g model.step

Example 4. Import only the solid-oriented content of a mixed model

step-g --skip-open-shells -o solids.g mixed.step