' The material property of GeometryModel3D specifies the material applied to the 3D object.  
' In this sample the material applied to the 3D object is made up of two materials layered  
' on top of each other - a DiffuseMaterial (gradient brush) with an EmissiveMaterial 
' layered on top (blue SolidColorBrush). The EmmisiveMaterial alters the appearance of  
' the gradient toward blue.

' Create a horizontal linear gradient with four stops.   
Dim myHorizontalGradient As New LinearGradientBrush()
myHorizontalGradient.StartPoint = New Point(0, 0.5)
myHorizontalGradient.EndPoint = New Point(1, 0.5)
myHorizontalGradient.GradientStops.Add(New GradientStop(Colors.Yellow, 0.0))
myHorizontalGradient.GradientStops.Add(New GradientStop(Colors.Red, 0.25))
myHorizontalGradient.GradientStops.Add(New GradientStop(Colors.Blue, 0.75))
myHorizontalGradient.GradientStops.Add(New GradientStop(Colors.LimeGreen, 1.0))

' Define material that will use the gradient.
Dim myDiffuseMaterial As New DiffuseMaterial(myHorizontalGradient)

' Add this gradient to a MaterialGroup.
Dim myMaterialGroup As New MaterialGroup()
myMaterialGroup.Children.Add(myDiffuseMaterial)

' Define an Emissive Material with a blue brush.
Dim c As New Color()
c.ScA = 1
c.ScB = 255
c.ScR = 0
c.ScG = 0
Dim myEmissiveMaterial As New EmissiveMaterial(New SolidColorBrush(c))

' Add the Emmisive Material to the Material Group.
myMaterialGroup.Children.Add(myEmissiveMaterial)

' Add the composite material to the 3D model.
myGeometryModel.Material = myMaterialGroup