Found a neato thing... not sure if anyone else does this or not so I thought I'd share.

I always hated having to use alpha map to block out areas that I don't want grass (under driveways, foundations, etc). I started tinkering with using the RayCast Geometry node to generate a weight map and BAM!
Nice and clean clipping of the instances with no maps or extra geometry needed.

Click image for larger version. 

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