Irrlicht Engine

Thanks!
It looks like someone figured it out in Unity using a vertex+fragment shader and stencil buffers, here's the post:
https://mispy.me/unity-alpha-blending-overlap/

What I desperately need from this community is guidelines to do the following (because I really can't find my way around this ...

Hi! I'm pretty new to irrlicht and loving it so far, I'm making a brush sketching tool and I got stuck on this issue:

I'd like for each of my strokes to never show overlapping alpha with itself, thus avoid the artifacts visible in this image:
https://i.stack.imgur.com/s5yqV.png

What I'd like to ...