You can make a copy of the ‘sample texture’ module and hack it a bit to return the red channel from the texture ( it’s easy ). It does already return the color, and I suspect you’re supposed to be able to crack the red channel out of that, but I don’t find the parameter settings very intuitive in Niagara, so I did this to it:
which gives me back the red channel:
which is what your landscape is using to do the height map.
Then you know to only spawn the particles if the red channel is white. You have to get the UVs right, of course, so what you’re seeing in the Niagara system matches with the landscape.