[RESOLVED] helix toolkit on .net core reference iusse

I'm trying to port a .net framework app to .net core (3.1), so I get the packages from nuget helixtoolkit, helixtoolkit.core.wpf and helixtoolkit.core.sharpdx. But the regefence in xaml, that I copied here: http://docs.helix-toolkit.org/en/lat...t-to-your-xaml is not correct. errors desappear if I reference xmlns:HelixToolkit="http://helix-toolkit.org/wpf", but app not show anything and crash. What am I missing?
here the xaml:

Code:

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<UserControl x:Class="UCGraph3D"
            xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
            xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
            xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
            xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
            xmlns:local="clr-namespace:Graph2k_Motors_Core"
                xmlns:HelixToolkit="http://helix-toolkit.org/wpf"
            mc:Ignorable="d"
              d:DesignHeight="685" d:DesignWidth="1277"  Background="#ff323130">
    <Grid>
        <HelixToolkit:HelixViewport3D Name="myviewport" ZoomExtentsWhenLoaded="True"  Background="Black"  ShowCoordinateSystem="True" >
            <!-- Remember to add light to the scene -->
            <HelixToolkit:SunLight/>
            <ModelVisual3D>
                <ModelVisual3D.Content>
                    <GeometryModel3D x:Name="myGeometryModel3D">

                        <GeometryModel3D.Geometry>
                            <MeshGeometry3D x:Name="myMeshGeometry3D"
                 
                                            TextureCoordinates="0.5 0.8 2 3 ">



                            </MeshGeometry3D>
                        </GeometryModel3D.Geometry >
                        <GeometryModel3D.Material>
                            <MaterialGroup>
                                <DiffuseMaterial>
                                    <DiffuseMaterial.Brush>

                                        <LinearGradientBrush StartPoint="0,0.5" EndPoint="2,2">
                                            <LinearGradientBrush.GradientStops>
                                                <GradientStop Color="green" Offset="0.1" />
                                                <GradientStop Color="yellow" Offset="0.5" />
                                                <GradientStop Color="red" Offset="1" />
                                                <GradientStop Color="Blue" Offset="2" />
                                            </LinearGradientBrush.GradientStops>
                                        </LinearGradientBrush>
                                    </DiffuseMaterial.Brush>
                                </DiffuseMaterial>
                            </MaterialGroup>
                        </GeometryModel3D.Material>
                    </GeometryModel3D>
                </ModelVisual3D.Content>
            </ModelVisual3D>



            <HelixToolkit:GridLinesVisual3D x:Name="mygridX"  Width="10" Length="10" MinorDistance="1" MajorDistance="1" Thickness="0.01" Fill="#FF03F921"  LengthDirection="1,0,0" Normal="0,0,1"/>
            <HelixToolkit:GridLinesVisual3D x:Name="mygridY"  Width="10" Length="10" MinorDistance="1" MajorDistance="1" Thickness="0.01" Fill="#FF03F921" LengthDirection="0,0,1" Normal="1,0,0"/>
            <HelixToolkit:GridLinesVisual3D x:Name="mygridZ"  Width="10" Length="10" MinorDistance="1" MajorDistance="1" Thickness="0.01" Fill="#FF03F921" LengthDirection="1,0,0" Normal="0,1,0" />

            <HelixToolkit:BillboardTextVisual3D Position="11 0 0" Text="X" Foreground="Yellow"/>
            <HelixToolkit:BillboardTextVisual3D Position="0 11 0" Text="Y" Foreground="Yellow" />
            <HelixToolkit:BillboardTextVisual3D Position="0 0 11" Text="Z"  Foreground="Yellow"/>
        </HelixToolkit:HelixViewport3D>
    </Grid>
</UserControl>

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I solved! It was a VGA driver problem(I was running in a VMWare VM taht use vmware graphics driver, changing drivers, or running outside the VM it work fine.