[Solved] [Help] "Select Slope" material function for landscape?

The If creates a hard mask though, so not the best way to achieve this unless you need it specifically like that.

To fade the masks you would have to use a map range.
if you *2PI the dot result you get the degree value.
To save on render cost you could just go the other way around. Adapt to the dot value.

map range clamped will output a mask that can be fed directly into a lerp.