Is it possible to mask UMG Blur effect introduced in 4.15? As I understood it takes all the parent container to apply blur.
But we have rectangular windows with sliced colors, and we are trying to make their background blurred. is it possible to blur the region only with alpha > 0 ?
Here is the picture what we try to achieve - blured rectangle masked by some mask (bottom - rectangle with corner circle cuts.)
I’m not sure I understand your question (a sample image of what you need would help). As I understand it, you want to blur the rectangular windows with sliced colors only? I guess you can make that a standalone widget (which u’ll add to the main widget) and set the blur only there.
Top is what we can do now, blur a rectangle (on the left is blur result, on the right - blur mask)
Bottom - is what we are trying to achieve - a rectangular area with circle cut angles, and it’s mask on the right.
(but actually our mask looks a little bit different, but I struggled to draw it in paint.net )
Now it’s a lot clearer. Don’t know it that is actually possible (it’s also quite new feature). Maybe someone more into it can help you, sorry mate 
Did you ever figure this out Yata? Thanks!
The background blur widget in UE5 supports adjusting Corner Radius. If you want to apply a mask to control the blur region, see this plugin: https://youtu.be/XiJF8kqHW9c
