Chart3D Direct3D Rendering (previous rendered image remains)

Hi,

I tried WPF Chart3D Direct3D Rendering.
The performance was really nice. By the way, I got a problem and don’t know how to resolve it.
When rendermode is Direct3D, the previous rendered image is not cleared when new rendered image is generated with rotating or switching view mode.
I attached the captured image which is generated with switching view mode (initial 3D => 2D => 3D)

You can see the phenomenon as follows with the sample project in the blog

http://our.componentone.com/2013/12/16/visualize-surface-charts-in-wpf-with-direct3d-rendering

1. change mode ;
ChartType => SurfaceZone
Render Mode => Direct3D
2. Click 2D X-Y button
3. Click 3D Deafult buttton

1. change mode ;
ChartType => SurfaceZone
Render Mode => Direct3D
2. Rotate with mouse

Thank you in advance for your support.