Can you make a simple blend file that demonstrates this issue?

I made a simple blend file but the behavior is a little different, the white foreground GPlines dissappear when over a dark BG GP object and a blur visual effect applied.

If you look at it from the side you can see the white lines that are not affected by the blur effect a little bit.

Also I opened my main problem blend file on an nvidia 1080 windows 10 machine and the problem exists there too.

I have tested and the blur works with overlap objects. We need a simple file to reproduce the problem or to verify if this is a technical limitation.

Anyway, I think this is related to T59425.

@Tom Nelson (tomnel) Anyway, while we fix the z-depth problem (T59425), you can fix it separating the rain in a new GP object and verifying the rain origin is in front of other objects origin (it's the same where are the strokes, the important is where is the origin).

Thanks Antonio,
There is a simple blend file attached above. In it there are two GP objects, a black circle and in front of the circle a bunch of white lines with a blur effect.
For me the white lines disappear or lose the blur effect when in front of the dark circle GP object.
That doesn’t show up for you?

I will check again but I believe the origin of the lines is in front of the dark circle.

@Tom Nelson (tomnel) I see now the problem, it looks the z-depth is not working as expected when apply blur.

@Tom Nelson (tomnel) Try to change the depth ordering of the rain to Front.

I need investigate about this, it looks a precision problem when use blur because the blured areas are too "low" values and the code is clipping it.

Setting the depth ordering worked for the viewport (thanks!), but not the render output.
Taking a close look at the render it looks like the blur is ok but the opacity is not so where the rain overlays another GP object the opacity jumps to 100%

I am using a GP modifier to lower the opacity

I have done some changes in 0d7fe55d0e76 commit. You don't need put in Front.

Still need to improve render.

Can confirm, working in viewport, not in render. thanks!