how can I remove background color from a material?

[anonymous_user_818df549]

Thank u very much!
I found a solution on github: GitHub - Tolc/Unreal-UMG-3DObjectInWidget: A simple Unreal Engine 4 project (precisely 4.7.4) showing how to render a 3D object/mesh in a UMG widget..

But this solution generates noticeable aliasing，how can I solve this problem? Thank u.