remove wpf reference

Pilz.Drawing.Drawing3D.OpenGLRenderer/Preview/ModelPreview.vb

@@ -9,6 +9,7 @@ Imports Point = System.Drawing.Point
 Imports KeyboardState = OpenTK.Input.KeyboardState
 Imports Keyboard = OpenTK.Input.Keyboard
 Imports Key = OpenTK.Input.Key
+Imports Color = System.Drawing.Color
 
 Namespace PreviewN
 
@@ -25,12 +26,22 @@ Namespace PreviewN
         Private _isMouseDown As Boolean = False
         Private isDeactivated As Boolean = False
         Private ReadOnly myModels As New Dictionary(Of Object3D, Renderer)
+        Private WithEvents RenderTimer As New Timers.Timer(1) With {.AutoReset = True}
 
         Public Property RenderWhenWindowsIsInactive As Boolean = False
         Public Property EnableCameraControlling As Boolean = True
         Public Property Scaling As Single = 500.0F
         Public Property ClearColor As Color = Color.CornflowerBlue
 
+        Public Property RenderInterval As Double
+            Get
+                Return renderTimer.Interval
+            End Get
+            Set
+                renderTimer.Interval = Value
+            End Set
+        End Property
+
         Public ReadOnly Property Camera As Camera
             Get
                 Return MyCamera
@@ -111,7 +122,7 @@ Namespace PreviewN
             Me.glControl1.VSync = False
             Me.Controls.Add(Me.glControl1)
             Me.ResumeLayout(False)
-            AddHandler Windows.Media.CompositionTarget.Rendering, AddressOf CompositionTarget_Rendering
+            renderTimer.Start()
 
             Scaling = scale
 
@@ -194,7 +205,7 @@ Namespace PreviewN
             isDeactivated = True
         End Sub
 
-        Private Sub CompositionTarget_Rendering(sender As Object, e As EventArgs)
+        Private Sub RenderTimer_Elapsed(sender As Object, e As Timers.ElapsedEventArgs) Handles RenderTimer.Elapsed
             If Not isDeactivated OrElse RenderWhenWindowsIsInactive Then
                 RaiseEvent WandUpdateView()
                 glControl1.Invalidate()