v0.3.0

Version 0.3.0 builds the viewer on the scene model of the IOScene package
(IOScene [0.1.0, 0.2.0-0.0), a new dependency of the IOViewer package). This is a breaking change of the
library API. What breaks for existing users:

1. The model types move to namespace IOScene with Scene* names, ViewerClash* included; doc.Elements becomes
   doc.Scene.Elements, and the members in the table below change.
2. The documented quick start (a ViewerMesh with its own vertices) becomes SceneDocument.AddMesh.
3. Written JSON has a new shape. IOViewer 0.2.0 reads a 0.3.0 file as an empty document with exit code 0, because it
   ignores unknown members.
4. A page regenerated from an old snapshot shows each mesh without an element as an element (in the element count, the
   tree and hide).

Not broken: loading 0.1/0.2 JSON, existing HTML pages, the ioviewer arguments, the importer to exporter pipeline
(GlbViewerImporter to HtmlViewerExporter, ViewerDocument.Title) and the one-package install (IOScene comes with
the IOViewer package). The IOViewer.Cli tool only gains inputs.

Migration from 0.2.0

0.2.0 (IOViewer.Model)	0.3.0
Vector2d, Vector3d, BoundingBox3d, Transform3d, RgbaColor	the same names in namespace IOScene
Vector4d, Quaterniond	removed, no replacement
ViewerDocument.Elements, Meshes, Geometries, Materials, Textures, Viewpoints, ClashTests	ViewerDocument.Scene.Elements, Instances, Geometries, Materials, Textures, Viewpoints, ClashTests
ViewerDocument.SourcePath, Author, CreatedAt, Application	Scene.Models[0].Path, Author, CreatedAt, Application
ViewerDocument.Grids (one grid system)	Scene.Grids (a list of SceneGridSystem, each with ModelId)
ViewerDocument.TimeLiner	Scene.Schedules (a list of SceneSchedule)
ViewerDocument.LinkedFiles (ViewerLinkedFile Name, Path, Visible)	Scene.Models (SceneModel with a unique Key, Name, Path); Visible = false is the model's key in ViewerDocument.HiddenModelKeys
ViewerDocument.BoundingBox, ComputeBoundingBox()	Scene.ComputeBounds()
ViewerDocument.Title (default 3D BIM Model)	kept; it reads and writes Scene.Title (default empty)
ViewerDocument.SectionPlanes, SectionBox, ViewerSectionPlane, ViewerSectionBox	kept; their Vector3d is IOScene.Vector3d
-	ViewerDocument.Scene, ViewerDocument.HiddenModelKeys, new ViewerDocument(SceneDocument)
ViewerElement	SceneElement
ViewerElement.LinkName	SceneElement.ModelId, the id of a SceneModel
ViewerElement.Level (a string)	SceneElement.LevelId, the id of a SceneLevel in Scene.Levels
ViewerElement.Properties, AddProperty(group, name, value)	ScenePropertySet in Scene.PropertySets (Name = group), referenced by SceneElement.PropertySetIds; each SceneProperty has a SceneValue (SceneValue.FromText for a string)
ViewerElement.MeshIndices, ViewerElement.BoundingBox	removed; SceneInstance.ElementId links an element to its geometry
ViewerMesh	SceneInstance, which places a SceneGeometry for an element
ViewerMesh.Vertices, Indices, Normals, UVs (own geometry)	a SceneGeometry placed by one instance; SceneDocument.AddMesh adds both and the element
ViewerMesh.ElementId (optional)	SceneInstance.ElementId (required: every instance belongs to an element)
ViewerMesh.GeometryId, Transform, MaterialId, Name	SceneInstance.GeometryId, Transform, MaterialId, Name
ViewerMesh.Color, ViewerMesh.Opacity, ViewerMaterial.Opacity	the alpha of SceneInstance.Color or SceneMaterial.Color, the only opacity
ViewerMesh.TextureIndex, ViewerMaterial.TextureIndex	SceneMaterial.TextureId, the id of a SceneTexture
ViewerMesh.Id, BoundingBox, ComputeBoundingBox()	removed
ViewerGeometry	SceneGeometry, with Topology (Triangles, Lines, Points); empty Indices means non-indexed
ViewerMaterial	SceneMaterial
ViewerTexture (Base64Data string)	SceneTexture (Data bytes)
ViewerGridSystem, ViewerGridLine	SceneGridSystem, SceneGridLine
ViewerViewpoint, ViewerCamera, ViewerProjection	SceneViewpoint, SceneCamera, SceneProjection
ViewerTimeLinerSchedule	SceneSchedule; GetOverallStart() and GetOverallEnd() are removed
ViewerTimeLinerTask, ViewerTimeLinerTaskType	SceneTask, SceneTaskType
ViewerTimeLinerTask.AttachedElementIds	SceneTask.ElementIds
ViewerTimeLinerTask.AttachedSetName	removed
ViewerClashTest, ViewerClashResult, ViewerClashStatus	SceneClashTest, SceneClashResult, SceneClashStatus
ViewerClashResult.Distance (double)	SceneClashResult.Distance (double?, null when the source does not report it)
constructors with parameters (new ViewerViewpoint(name, camera) and others)	object initializers

Added

• HtmlViewerExporter.Save, Export and ExportToString take a SceneDocument too.
• JsonViewerImporter and the ioviewer tool read three kinds of JSON: viewer JSON ("Kind": "ioviewer"), IOScene
  scene files ("Kind": "ioscene") and IOViewer 0.1/0.2 snapshots (no Kind). In a snapshot, meshes that share an
  ElementId no element has get one element with that id, and each other mesh without an element gets one of its own.
  A newer format, a missing or wrong Format and an unknown kind are rejected with InvalidDataException.
• The HTML viewer shows SceneElement.SourceId, the element's id in its source format (such as a Revit UniqueId or an
  IFC GlobalId), as its own row in the properties panel ("Source ID" / "ID источника"), and the model tree search finds
  it. It is written to the page's element list only when set.
• The ioviewer tool reads IFC (.ifc, .ifczip) through IfcIO.Scene 0.11.1 and Revit (.rvt) through
  RvtIO.Scene 0.4.0. The model key is the file name; the title is the IFC project name, or the Revit file name. What
  the engine could not convert (such as an element without geometry) is printed to standard error as one warning or
  error per kind with its count. When the engine reported an error (elements may be missing), the requested output
  (the page, the JSON or both) is still written and the tool exits with code 4. The IOViewer library still references no engine; only the IOViewer.Cli tool
  package ships IfcIO, RvtIO and their dependencies (see THIRD-PARTY-NOTICES.md).

Changed

• JsonViewerExporter writes viewer JSON format 2: { "Kind": "ioviewer", "Format": 2, "Scene", "SectionPlanes", "SectionBox", "HiddenModelKeys" }, with the scene in the encoding of IOScene's SceneJson.
• GlbViewerImporter and ObjViewerImporter return documents whose scene has one model and passes
  SceneDocument.Validate().
• The viewer draws triangles only: instances of line or point geometry are skipped, and the ioviewer tool prints a
  warning with their number.
• Opacity is a colour alpha byte, so an opacity that is not a multiple of 1/255 is rounded (0.35 becomes 89/255).
• In an IOViewer 0.1/0.2 snapshot, an element LinkName that matches no linked file becomes a model of the scene, so
  a page made from the snapshot lists it in the linked files panel, where its elements can be hidden.
• The documentation states the model's units and axes: all coordinates and lengths are in metres, with Z up.
• A clash distance is nullable. The page writes null for a distance the source does not report and the clash list
  shows no distance for it, where it showed 0. A 0.1/0.2 snapshot keeps the distance it has (0 when it has none).
• GlbViewerImporter converts a material's base colour factor from glTF's linear values to sRGB. Imported GLB colours
  look lighter than in 0.2.0, which is now correct. The alpha stays linear; every channel is now rounded to the nearest
  byte, where it was truncated.
• A 4D task of a type this version does not know is shown as a construct task; it was left out of the schedule.
• The properties panel shows the property sets of an element that have the same name as one group, and a property name
  that repeats in a group gets a numbered suffix (Height (2)), so no property is lost. Elements that share an id,
  which SceneDocument.Validate() rejects, show the properties of all of them.