I am trying to apply this technique to simple planar walls, so no UV mode used.
The scattering itself works.
I then need to limit it to a boundary, but the Edge mode doesn't work. According to the tutorial it should :
Let's start by taking a look at how to scatter of vertical planar areas, which has the advantage of retaining all of Forest Features including edge mode, spline painting and more.
I set it up as I would for any FP : add the spline to the Areas list, deactivate the Surface Area and check "Edge" in Boundary Checking. Is there anyhting else to ado when dealing with a vertical surface ?