GPU Grass is a replacement for Unity's terrain detail system.

Unity Asset Store Page

While building a forest scene in Unity I found that I couldn't get the look and performance I wanted from Unity's terrain grass and decided to make my own system to use instead. What I thought would be a quick tool turned into months of research and rewrites. I finally came up with GPU Grass which I think is a very fast way to place and render good looking grass on terrain in Unity.

GPU Grass doesn't have all of the features that's Unity's system does but it is much faster and in my opinion better looking.