cadmpeg-ir

cadmpeg-ir defines the format-neutral document exchanged by cadmpeg codecs. It provides the CadIr data model, codec interfaces, validation, structural diffing, JSON serialization, and explicit representations of source fidelity and decode loss.

Install

cargo add cadmpeg-ir

Model

A CadIr document contains:

required IR version 4 schema, including loop boundary roles, vertex loops, ordered pcurve uses, and the subds arena;
canonical units and document tolerances;
flat, ID-referenced arenas for topology, geometry, subdivision control cages, construction features, tessellation, appearance, and source attributes;
sparse provenance and exactness annotations;
independently versioned source-native namespaces;
retained records whose bytes could not be mapped to typed entities.

The topology graph follows body → region → shell → face → loop → coedge → edge → vertex. Faces reference surface carriers, edges reference curve carriers, coedges may reference parameter-space curves, and vertices reference points. IDs are globally unique within a document. The subds arena stores free Catmull–Clark control cages: directed face edge uses must form closed, endpoint-continuous rings, and edge sharpness is stored independently at each endpoint. Arena order is canonical after CadIr::finalize; every arena is sorted lexicographically by entity ID. Free surface, curve, subdivision-surface, and tessellation carriers can retain a SourceObjectAssociation for native object identity and effective display metadata.

Coordinates and linear quantities use millimeters. Angular quantities use radians. Constructors do not enforce document invariants; call validate after construction or transformation.

Construct and consume a document

Create and validate an empty current-version document:

use cadmpeg_ir::units::Units;
use cadmpeg_ir::{validate, CadIr};

let mut ir = CadIr::empty(Units::default());
// Populate ir.model arenas and use typed IDs to connect entities.
ir.finalize();
let report = validate(&ir, Vec::new());

assert!(report.is_ok());
assert_eq!(ir.ir_version, cadmpeg_ir::IR_VERSION);

CadIr::to_canonical_json emits pretty JSON after the caller establishes canonical arena order. CadIr::from_json parses only ir_version: "4". The version-4 schema requires model.subds. diff compares units, tolerances, annotations, and entity arenas by stable identity.

Format crates implement the object-safe Codec trait. A consumer can select a codec by detection confidence, inspect a container without decoding geometry, then decode the selected source:

use cadmpeg_ir::{Codec, Confidence};

fn accepts(codec: &dyn Codec, prefix: &[u8]) -> bool {
    codec.detect(prefix) >= Confidence::Medium
}

DecodeResult contains the finalized document, a DecodeReport, and a SourceFidelity sidecar for provenance, conversion exactness, and retained native records. CodecError represents operation failure such as wrong format, malformed container, unsupported capability, or I/O failure. Successful decoding can still be incomplete: LossNote records transferred information that was approximated or omitted, while UnknownRecord retains an uninterpreted source record by location, digest, links, and optional bytes.

Entity and field fidelity belongs in sidecar Annotations. Missing exactness entries mean byte-exact. Other entries distinguish deterministic derivation, inference, and unknown origin. Provenance entries identify source streams and byte offsets.

Scope

IR version 4 covers B-rep topology, analytic and NURBS geometry, Catmull–Clark control cages, procedural construction links including Sum and bounded Revolution definitions, planar and spatial sketches, tessellation, appearance, attributes, and neutral feature records. Native namespaces retain format-specific design and history records. Assembly instancing through components, occurrences, and joint constraints, together with drawings, semantic annotations, spreadsheets, and presentations, extend the neutral model.

Documentation