Change color (material) of STL model loaded by helix toolkit. Can't convert from Model3DGroup t-CodePudding

I would like to change color of 3D model loaded from .stl file.

Problem is that it is loaded as Model3DGroup. Model3DGroup has no property material which allows to change color. I tried to convert Model3DGroup to GeometryModel3D (it has material property). Geometry is empty after conversion and viewport is showing nothing.

What can I improve in this code to be able to change color of model from stl file? Maybe is there another way to make it?

I found simillar issue here also without solution, so maybe this time someone could help. Helix 3d-toolkit Displayed .STL model color change

XAML:

         <helix:HelixViewport3D x:Name="viewPort3d" ZoomExtentsWhenLoaded="True">
                <helix:DefaultLights/>
                <ModelVisual3D  x:Name="ViewPortModel" Content="{Binding Actual3dModel}"/>
         </helix:HelixViewport3D>

C#:

     private Model3DGroup actual3dModel;

     public Model3DGroup Actual3dModel
         {
            get {
                    return actual3dModel;
                }

            set
                {
                    actual3dModel = value;
                    OnPropertyChanged("Actual3dModel");
                }
            }
   
      private void LoadModel()
            {
                var importer = new HelixToolkit.Wpf.ModelImporter();
                var model = importer.Load("Assets/Model.stl");
             
                var m0 = (MeshGeometry3D)((GeometryModel3D)model.Children[0]).Geometry;
                var outsideMaterial = MaterialHelper.CreateMaterial(Colors.Red, 0.1);
                var insideMaterial = MaterialHelper.CreateMaterial(Colors.Blue);
                var modelGroup = new Model3DGroup();

                modelGroup.Children.Add(new GeometryModel3D { Geometry = m0, Material = outsideMaterial, BackMaterial = insideMaterial });
                Actual3dModel = modelGroup;
            }

Tried also in this way (again empty model is shown).

        private void LoadModel2()
        {
            this.dispatcher = Dispatcher.CurrentDispatcher;
            var loader = new ModelImporter();
            var model = loader.Load("Assets/Model.stl", this.dispatcher);
            GeometryModel3D gmodel = model.Children[0] as GeometryModel3D;

            DiffuseMaterial material = new DiffuseMaterial(new SolidColorBrush(Colors.Red));
            gmodel.Material = material;
            gmodel.BackMaterial = material;
          
            var modelGroup = new Model3DGroup();
            modelGroup.Children.Add(gmodel);
           
            Actual3dModel = modelGroup;
        }

CodePudding user response：

Model3DGroup contains a group of GeometryModel3D. Material property is in GeometryModel3D. You need to change GeometryModel3D.Material.

CodePudding user response：

I've found solution. I dont know why but changing model.Children[0] to model.Children[1] solved issue.

Now model is shown and material color is changed.