Question: IFC 3D Visualization pipe line

[Noranius]

I want to add the visualization of textures in xBIM. This feature is necessary to support the visualization of IfcSurfaceTexture and sub classes. I have chosen to understand how the visualization of the model works first. What I have understood until now is that the model is loaded (IfcStore.Open) and after that the DrawingControl3D cares about the 3D visualization. Further, the Scene is created as SurfaceLayerStyle. I stuck at that point.

The method SurfaceLayerStyler.BuildScene(...)creates a scene, on top of the model. However, that scene is never touched again, only returned at the end. I guess other calls upon the model affect the scene, don't they?

I have not seen any call to the Canvas (HelixViewport3D) in the DrawingControl3D. How get the xBIM shape data transformed and handed over to the HelixViewPort3D?

Thanks in advance
Noran

[Noranius]

Any Help on this topic?

[CBenghi]

Hi @Noranius,

have a look at the 'AddLayerToDrawingControl' function in DrawingControl3D.
There's where the elements get added to the tree of elements in the viewer:

 if (layer.Style.IsTransparent)
   Transparents.Children.Add(mv);
else
   Opaques.Children.Add(mv);
end if

Is this what you were after?

[bekraft]

Concerning textures in IFC: There's similar question maybe associated to yours:
xBimTeam/XbimGeometry#183

The tesselation pipeline is staged. So far, your are right. The data is never changed. Any update to the geometry means to reload the whole scene. The WPF UI only uses a readonly view on a binary encoded geometry representation based on triangulation.

So far I understood the visualization pipeline:

• OCC builds up the fundation of geometry modelling wrapped by some Xbim features (i.e. XbimFace)
• Tesselation is done partially in OCC partially by tesselation algorithm (LibTess wrapped in XbimEssentials)
• Handover to the UI is done in binary chunks (encoded in XbimShapeGeometry)
• Reimport is done by the presentation layer in WpfMeshGeometry3D
  

  XbimWindowsUI/Xbim.Presentation/WpfMeshGeometry3D.cs

  Line 724 in 0b37425

  public void Read(byte[] mesh, XbimMatrix3D? transform = null)

  having the knowledge of placement nodes in prior
• It hands the visualization over to the WPF presentation

Last:

• The geometry representation is encapsulated into the Media3D scene description. There's no direct call to any drawing method

[Noranius]

The last week i got to work on this. What I searched for is not in the XbimWindowsUI, it is in XbimGeometry repository. When the Xbim3DModelContext is created in the main Window.

XbimWindowsUI/XbimXplorer/XplorerMainWindow.xaml.cs

Line 281 in 13bb09a

context.CreateContext(worker.ReportProgress, true);

Within this method all 3D objects are created for visualization. Hence, I have to step in this part of the XbimGeometry repo.

https://github.com/xBimTeam/XbimGeometry/blob/8c5db8c8ea02662bfac6639b6136d478471b62cf/Xbim.ModelGeometry.Scene/Xbim3DModelContext.cs#L680

to be continued...

[Noranius]

The next point is where are the textures loaded:
The textures are loaded within the XbimTexture.cs within https://github.com/xBimTeam/XbimEssentials
https://github.com/xBimTeam/XbimEssentials/blob/cb6bfe1440201d8bf3f9ae1922635274011dacfc/Xbim.Ifc/XbimTexture.cs#L38
This method has to be extended by another Case
if (style is IIfcSurfaceStyleWithTextures) AddTexture((IIfcSurfaceStyleWithTextures)style);
I'm on it, o implement the method AddTexture.

Second the texture has to be transformed for that I'm on to implement the necessary methods, which generate the materials from the image textures within the WpfMaterial.

XbimWindowsUI/Xbim.Presentation/WpfMaterial.cs

Line 10 in 13bb09a

public class WpfMaterial : IXbimRenderMaterial

Pull requests will follow, when all is ready.

[Noranius]

Finally the problem is solved an xBIM is now capable to display textures. Refer to #163.