Picture save wo background

Hello,

I am using CSS 2017x; does anybody know a way to save a 2D picture direkt out of 3DX ( hardware shade) in format PNG, TIF,etc, where the background is transparent. ( alpha chanel)

I am used to do this out of solidworks all the time and I am sure there is a way in 3DX, but I didn´t find it, yet.

Thanks in advance for any advice.