IOScene

IOScene is a neutral scene model for tessellated BIM and CAD data, with a JSON file format and a structural validator. It is the shared contract between the readers of source formats and the tools that show or check a model: a reader turns its own model into a SceneDocument, and a viewer, a clash tool or a writer of another format takes it from there. The package is pure managed .NET (8 and 10) and has no dependencies.

Built clean-room under the IOExtend organization.

Status: preview. The model is specified in docs/contract.md; names and members may still change before 0.1.0.

What is in a scene

• Elements in a flat list with a parent link, a source id and an optional IFC GlobalId; an element may have no geometry.
• Geometry stored once and placed by instances with an affine transform; triangles, lines and points, indexed or not.
• Materials with colour, roughness, metalness and an optional texture.
• Typed property values with a display string, a number in SI units and a stable key; property sets are shared by id.
• Models (source files and links), levels, grids, saved viewpoints, 4D schedules and clash results.
• SceneJson reads and writes the file ("Kind": "ioscene", "Format": 1), and Validate() checks the structure.

Everything is in metres, right-handed, Z up, in one coordinate space per document.

A scene holds what a viewer or a coordination tool shows, filters, measures or tests. It is not an authoring model: parametric geometry, B-rep and type objects stay in the source formats' own libraries, and no source file is rebuilt from a scene.

Install

dotnet add package IOScene --prerelease

A package that depends on IOScene references one 0.x line, because a 0.x minor release may break the API and a patch release never does. For the line 0.N the range is [0.N.0, 0.N+1.0-0); the -0 keeps out the previews of the next line:

<PackageReference Include="IOScene" Version="[0.1.0, 0.2.0-0)" />

During the preview the lower bound is the preview: [0.1.0-preview.2, 0.2.0-0). dotnet pack reports NU5104 for a stable package with such a range; add <NoWarn>$(NoWarn);NU5104</NoWarn> to the referencing project.

Quick start

One mesh into a scene file:

using IOScene;

var scene = new SceneDocument { Title = "Quad" };
scene.AddMesh(
    "Quad",
    [new(0, 0, 0), new(1, 0, 0), new(1, 1, 0), new(0, 1, 0)],
    [0, 1, 2, 0, 2, 3],
    new RgbaColor(200, 80, 80));

foreach (var issue in scene.Validate())
    Console.WriteLine($"{issue.Severity} {issue.Code}: {issue.Message}");

SceneJson.Save(scene, "quad.json");

AddMesh creates the model, the geometry, the element and the instance that links them. A reader of a real format fills the same lists directly: Models, Geometries, Elements, Instances, PropertySets and the rest. SceneJson.Load brings the file back. SceneJson.Write and SceneJson.Read work on streams and on JSON text.

Documentation

• docs/contract.md: purpose and invariants, every type, the decisions behind them, what is left out, how the contract changes, the file format, the validation codes and the unit grammar.
• docs/keys.md: the registry of property key namespaces and SourceFormat values.
• CHANGELOG.md, CONTRIBUTING.md and SECURITY.md.

License

MIT, see LICENSE.