cadmpeg-codec-f3d

Container-level codec for Autodesk Fusion 360 .f3d files.

What is implemented

A .f3d is a ZIP archive whose entries follow documented naming families (BREP streams, .protein material ZIPs, design/ACT/browser bulk & meta streams, manifests, previews). This codec:

• [F3dCodec::detect] recognizes the ZIP magic plus f3d marker strings;
• [F3dCodec::inspect] enumerates and classifies every entry and reads the ASM BinaryFile header of each BREP stream (magic/width, version words, product_family/product_version/save_date, scale/resabs/resnor) and locates the delta_state history boundary;
• [F3dCodec::decode] frames the active BREP's SAB record stream and builds the IR B-rep graph (body → region → shell → face → loop → coedge → edge → vertex → point) plus the analytic surface/curve carriers it references.

What is decoded, and what is reported as loss

The SAB record stream ([sab]) is framed token-by-token so record boundaries stay exact even across records this codec does not interpret. From that RecordTable ([brep]) it decodes the topology graph and the analytic carriers — plane, cone/cylinder, sphere, torus, straight line, ellipse/circle — with lengths converted centimetre→millimetre.

Cached spline/procedural surfaces and curves, UV pcurves, linked ASM attributes, body transforms, nested Protein appearance assets, and Design body assignments are transferred. Unsupported source records remain explicit in the [cadmpeg_ir::report::DecodeReport]. When the active stream is not a decodable BinaryFile8 SAB, decode falls back to container metadata.