IOExtend

Pure managed .NET libraries and cross-platform CLI tools for BIM and CAD interoperability.

Read, inspect, and convert building models and drawings without the authoring software, its API, or native libraries installed.

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IOExtend is a set of independent .NET engines, each reading one family of BIM or CAD formats, plus a neutral scene model and a standalone HTML viewer. Everything is managed code without native libraries, for use in CI/CD pipelines, web backends, and desktop engineering software.

Project	Primary Formats	Key Capabilities	Documentation	NuGet	Release	Brand Palette
RvtIO	.rvt, .rfa (Revit 2020–2026 tested, 2027 partial)	Elements, parameters, geometry, file metadata and project information, FilteredElementCollector queries, IFC2X3 and JSON export. Reads only; does not write Revit files				Amber #F2A33A
NwcIO	.nwc, .nwd, .nwf (Navisworks 2016–2026 tested)	Scene hierarchy, meshes, materials, GUIDs and properties; viewpoints and redlines; JSON export; writes .nwc. Frozen, bug fixes only: IFC2X3/IFC4, glTF, OBJ and HTML export, clash detection, grouping and matrix, HTML clash report, BCF 2.1, measure, grids, revision diff, TimeLiner, selection and search sets, appearance profiler, mesh clipper, Navisworks XML				Azure Blue #3B82F6
IfcIO	.ifc, .ifczip	Reads and writes ISO 10303-21 STEP for buildingSMART IFC2x3 CV 2.0 and IFC4, spatial hierarchy, properties and meshes, IfcApi facade, 5D cost schedules, IDS 1.0 audit, JSON export. Frozen, bug fixes only: HTML viewer, glTF/OBJ export, clash, measure, grids, diff, BCF 2.1, 4D work-schedule logic				Electric Violet #A855F7
DwgIO	.dwg (AutoCAD R2004, R2010, R2013, R2018)	Version detection (R13–R2018), section container and decompression, drawing metadata, thumbnail and handle map, LINE/CIRCLE/ARC/POINT geometry, JSON export. R13–R2000 and R2007 are planned				Sky Blue #38BDF8
PlaIO	.pla, .pln (Archicad 27, 29, 30), .bimx cover	File kind detection, container header, BL/DY block index, raw and zero-mask payload decoding, object directory search, BIMx PNG cover, text reports and directory JSON. Preview: elements, parameters and geometry are not read				Pink #EC4899

Project	Primary Formats	Key Capabilities	Documentation	NuGet	Release	Brand Palette
IOScene	Scene .json ("Kind": "ioscene")	Neutral scene model for tessellated BIM and CAD data: elements, instanced geometry, materials, typed properties, models, levels, grids, viewpoints, 4D schedules, clash results. Metres, right-handed, Z up. SceneJson reader/writer and Validate(). No dependencies. Preview: names may change before 0.1.0				Emerald #10B981
IOViewer	.glb, .obj, JSON → .html	One self-contained HTML file that works offline (three.js embedded): model tree and properties, view cube, up to six section planes or a section box, distance measurement, viewpoints and tour, clash results, 4D schedule player, Russian and English interface. Reads IOScene scene files from 0.3.0 (on main, not yet released)				Cyan #06B6D4

• Engines are leaves. RvtIO, NwcIO, IfcIO, DwgIO, and PlaIO each read their own format, and some also write it. No engine references another IOExtend package or a scene type.
• IOScene is the neutral contract. A scene holds what a viewer or coordination tool shows, filters, measures, or tests. It is not an authoring model, and no source file is rebuilt from it.
• Adapters live with their engine. <Engine>.Scene turns an engine's model into an IOScene SceneDocument. It ships on the engine's version and tag, depends on exactly that engine version, and uses only the engine's public API.
• Consumers depend on IOScene only. From 0.3.0 the IOViewer library references IOScene and no engine. Only command line tools combine several adapters.
• Frozen extras. Viewer, export, and coordination features inside IfcIO and NwcIO get bug fixes only. They stay available and are removed no earlier than that engine's 1.0, and only after a published replacement exists.

flowchart LR
  ifc[".ifc / .ifczip"] --> IfcIO
  rvt[".rvt / .rfa"] --> RvtIO
  nwc[".nwc / .nwd / .nwf"] --> NwcIO
  dwg[".dwg"] --> DwgIO

  IfcIO --> IfcIOScene["IfcIO.Scene"]
  RvtIO --> RvtIOScene["RvtIO.Scene"]
  NwcIO -.-> NwcIOScene["NwcIO.Scene (planned)"]
  DwgIO -.-> DwgIOScene["DwgIO.Scene (planned)"]

  IfcIOScene --> IOScene["IOScene<br/>scene model + JSON"]
  RvtIOScene --> IOScene
  NwcIOScene -.-> IOScene
  DwgIOScene -.-> IOScene

  IOScene --> IOViewer["IOViewer + ioviewer CLI"]
  IOScene -.-> IOCoord["IOCoord (planned)"]
  files[".glb / .obj / scene .json"] ---> IOViewer
  IOViewer --> html[".html viewer"]

  classDef rvt stroke:#F2A33A,stroke-width:3px
  classDef nwc stroke:#3B82F6,stroke-width:3px
  classDef ifcio stroke:#A855F7,stroke-width:3px
  classDef dwgio stroke:#38BDF8,stroke-width:3px
  classDef viewer stroke:#06B6D4,stroke-width:3px
  classDef scene stroke:#10B981,stroke-width:3px
  classDef planned stroke-dasharray: 5 5
  class RvtIO rvt
  class NwcIO nwc
  class IfcIO ifcio
  class DwgIO dwgio
  class IOViewer viewer
  class IOScene scene
  class NwcIOScene,DwgIOScene,IOCoord planned

Solid arrows are code that exists; dashed arrows are planned. PlaIO has no scene adapter.

Until the adapters ship, the released tools can be chained, using IfcIO's frozen GLB export: rvtio project.rvt project.ifc, then ifcio export project.ifc --glb scene.glb, then ioviewer scene.glb -o viewer.html.

Versioning. In 0.x a patch release is additive and a minor release may break. A dependent references one IOScene line as [0.N.0, 0.N+1.0-0) (during the preview [0.1.0-preview.2, 0.2.0-0)), and an adapter pins its engine as [X.Y.Z]. Releases go in order: IOScene, then the engines with their adapters, then IOViewer.

1. Pure Managed .NET:
   • No C/C++ native libraries (.dll, .so, .dylib).
   • Targets .NET 8 and .NET 10; the engine and viewer READMEs list Windows, Linux, and macOS as supported.
2. No Proprietary SDK Dependencies:
   • Works without Autodesk Revit, Autodesk Navisworks, AutoCAD, Archicad, or their APIs.
3. Clean-Room Specification:
   • Written independently from format analysis, ISO/buildingSMART standards, and documented specifications.
   • No decompiled or leaked source, no vendor headers or SDKs. The few open-source components, such as OpenMcdf and SharpZipLib in RvtIO and three.js in IOViewer pages, are listed in that repository's THIRD-PARTY-NOTICES.md.
4. Stated Scope:
   • Each README states the tested version range and what is not read or written; IfcIO and NwcIO also list their frozen features.

Install any of the libraries via the .NET CLI:

# Autodesk Revit engine
dotnet add package RvtIO

# Autodesk Navisworks engine
dotnet add package NwcIO

# buildingSMART IFC engine
dotnet add package IfcIO

# Autodesk DWG engine
dotnet add package DwgIO

# Archicad project container reader
dotnet add package PlaIO

# Neutral scene model (preview only so far)
dotnet add package IOScene --prerelease

# Standalone WebGL/HTML viewer generator
dotnet add package IOViewer

Every engine and the viewer ship a command line tool for CI/CD scripting; IOScene is a library only:

# Install the CLI tools globally
dotnet tool install --global RvtIO.Cli
dotnet tool install --global NwcIO.Cli
dotnet tool install --global IfcIO.Cli
dotnet tool install --global DwgIO.Cli
dotnet tool install --global PlaIO.Cli
dotnet tool install --global IOViewer.Cli

# Export a Revit project to IFC
rvtio project.rvt project.ifc

# Convert a Navisworks model to binary glTF
nwcio model.nwc model.glb

# Run clash detection over a folder of Navisworks models with BCF output
nwcio ./models --clash-bcf clashes.bcfzip --clash-tolerance 0.01

# Inspect an IFC model
ifcio info Building.ifc --report

# Inspect a DWG drawing
dwgio inspect drawing.dwg

# Inspect an Archicad project file
plaio info project.pln

# Generate a standalone HTML viewer from a GLB model
ioviewer model.glb -o viewer.html

Direct .ifc, .ifczip, and .rvt input for ioviewer is coming with the scene adapters (IOViewer#28, draft).

• All repositories in the IOExtend organization follow a clean-room policy.
• Repositories contain no confidential customer models, vendor files, or proprietary binaries.
• Tests that need real model files (RvtIO, NwcIO, DwgIO, PlaIO) read them from a local folder named by a *_TEST_FILES environment variable. CI does not set it, so those tests are skipped there.
• Every public code repository has a SECURITY.md. Report vulnerabilities through GitHub private vulnerability reporting (the repository's Security tab, Report a vulnerability), which is enabled in every public code repository. Please do not open a public issue for a security problem.