Thanks for the info, I see that now… Looks like there’s just not enough instance info available in materials. I’ve also tried getting instance forward vector by (1,0,0)->Transform Local to World and using it to calculate the offset somehow, but without luck.
What surprised me is that this is an old & common technique - billboard plane on the last LOD of instanced trees - but as we can see it’s very tricky (or impossible?) to do with materials in UE.
Well, I’ll try to figure out something but math is not my strongest side, unfortunately 