Setting Background of Viewport3DX to Transparent

Question

I am using the Viewport3DX from Helix Toolkit only to Draw into the Content2D Element. This works fine and very fast.

But the background is White and I would like to have an transparent background. I can set BackgroundColor to another color but not to Transparent. ALso the Background Property has no effect.

Is this normal issue is there an hidden option?

Answer 1

So now I know more. With EnableSwapChainRendering = true the viewport uses HWND to render in the WPF control and therefore there's no transparency. With EnableSwapChainRendering = false it renders to an D3DImage and transparency works.