Reference Adapters SolidworksFeatures

Relevant source files

The following files were used as context for generating this wiki page:

• src/convert/adapters/solidworks/resolved/Core.py
• re/Methodology.md
• re/solidworks/archive/Grammar.md
• re/solidworks/archive/Segmentation.md
• re/solidworks/features/Revolve.md
• src/convert/adapters/solidworks/core/Adapter.py

SOLIDWORKS Feature Resolution

SOLIDWORKS Feature Resolution identifies and extracts geometric modeling history from proprietary .SLDPRT and .SLDASM files. The system processes the Contents/Config-0-ResolvedFeatures stream to reconstruct a feature timeline, support planes, and sketches. It bypasses the Parasolid geometry cache (Contents/Config-0-Partition) to ensure that the extracted history represents the authoritative source of the model's design intent.

The resolution process relies on a cracked MFC-style su_CArchive serialization grammar. This grammar allows the project to perform object segmentation and map-index renumbering, which are necessary for structural edits such as inserting, deleting, or reordering features within the tree.

Serialization Architecture

The SOLIDWORKS feature stream uses su_CArchive, a byte-compatible clone of Microsoft Foundation Class (MFC) CArchive object serialization. The archive tracks a running map counter for every class definition and object instance.

Tag Grammar

The archive categorizes data using specific 2-byte tags:

| Bytes | Meaning | | :----------- | :---------------------------------------------------- | -------------------------------------------------- | | 00 00 | wNullTag — Represents a null object pointer. | | ff ff | wNewClassTag — Signals a new class definition. | | 0x8000 | i | Class Reference — Points to a class map index i. | | t < 0x8000 | Object Reference — Points to an object map index t. |

Map Counter Increment Rules

Maintaining the integrity of the archive during modification requires following precise increment rules for the map counter:

flowchart TD
    Start[Read Object Tag] --> ClassDef{Is ff ff?}
    ClassDef -- Yes --> Inc2[Increment Map +2]
    ClassDef -- No --> ClassRef{Is Tag & 0x8000?}
    ClassRef -- Yes --> Inc1[Increment Map +1]
    ClassRef -- No --> NullObj{Is Tag 0?}
    NullObj -- Yes --> Inc0[Increment Map +0]
    NullObj -- No --> Inc0

Loading

The map counter does not start at 1; it begins at a base value (e.g., 109, 110, or 111) depending on the number of features. These early indices represent objects and classes defined in preceding streams like CMgr or ModelHeader.

Feature Tree Structure (moCompFeature_c)

The moCompFeature_c record acts as the primary authority for the feature tree. It is a fixed-stride array that defines the sequence of features and links them to the swXmlContents/KeyWords oracle.

Entry Layout

Each entry in the array typically represents two nodes per feature: one for the sketch and one for the extrusion.

Offset	Width	Field	Description
End - 12	u32	Version	Constant 18000 (SOLIDWORKS 2025).
End - 8	u32	Node ID	Unique identifier matching KeyWords.
End - 4	u32	Timestamp	Unix time_t of the last modification.

Tree Rebuilding

The order of entries in the moCompFeature_c array determines the model's rebuild order. Swapping entry pairs in this array effectively reorders the feature tree in SOLIDWORKS, regardless of their physical positions in the binary stream.

Geometric Feature Resolution

The system resolves specific feature types by mapping binary markers to neutral geometric parameters.

Extrusion (Boss/Cut)

Extrusions are distinguished by their tree-node flag words and derived face-identity records. While 0x40000140 indicates a boss and 0x400201CA indicates a cut, the flag word alone is insufficient to change the operation; the operation is also implied by internal class bodies (moExtrusion_c vs moICE_c).

Feature Parameter	Binary Representation
Depth	Dimension-scalar record named D1 as float64 in meters.
End Condition	1-byte field at scalar - 818 (Blind=0, ThroughAll=1, MidPlane=6).
Reverse Direction	1-byte flag at scalar - 824.

Revolution

Revolutions use moRevolution_c (boss) or moRevCut_c (cut) classes. Unlike extrusions, switching between boss and cut for a revolve requires changing the class set, which alters all subsequent archive map indices.

sequenceDiagram
    participant D as Decoder
    participant S as Stream
    participant K as KeyWords
    D->>S: Find moRevEndSpec_c
    S-->>D: Constant 52-byte record
    D->>S: Resolve Axis at token - 131 or - 145
    S-->>D: Node ID + Timestamp
    D->>K: Validate Angle
    K-->>D: Angle in Degrees (e.g. 360°)
    D->>S: Read D1 Scalar
    S-->>D: Angle in Radians (float64)

Loading

The revolution axis is identified by a <u32 feature id><u32 time_t> pair found at a fixed offset relative to the moRevEndSpec_c object token:

• token - 145: Axis is a construction line inside a sketch.
• token - 131: Axis is a reference-axis feature.

Object Segmentation Logic

Segmentation is performed by tracing su_CArchive::ReadObject and su_CArchive::ReadClass calls in the swccu.dll module. This process recovers object boundaries by differencing consecutive buffer positions.

su_CArchive Internal Layout

Field offsets derived through runtime calibration:

• m_lpBufCur: 0x38 (Current buffer pointer)
• m_lpBufMax: 0x40 (Buffer end pointer)
• m_lpBufStart: 0x48 (Buffer start pointer)
• m_nMapCount: 0x50 (Archive map counter)

Validation of Segmentation

The correctness of the segmentation is proven by a symbolic re-emit process. The stream is parsed into a node list where all index references are converted to pointers. The model then re-computes indices and emits a new binary stream. If the emitted stream is byte-identical to the original input, the segmentation is verified as correct.

Summary of Derived Caches

SOLIDWORKS stores redundant geometric caches that are derived from authored parameters. These caches can often be left stale as the application recomputes them upon opening.

Cache Type	Binary Class	Responsibility
Bounding Box	moBBoxCenterData_c	Stores center coordinates and diameter.
Display Rectangles	moRefPlane_c	Stores UI visualization of planes.
Parasolid Blob	(Embedded)	Represents the supporting face surface.