I have been playing a lot in the terrain system the past few days, trying to understand the limitations. At first I implemented some terrain using TerrainComposer + RTP, and it looked great, but there were constant, subtle spikes in the FPS that I could not understand, so I put together a smaller project to test it. I have a used a fairly simple single terrain from a height map that I post-processed with terrain composer (without RTP/AFS). Adding grass at any decent constant density with a detail range of 80m will noticeably cause the spikes as you move (presumably as you arrive at the next visible patches) and it just gets worse as you increase the detail distance (presumably because more patches are viewable). Keep in mind that the frame rate when not spiking is at ~250-300fps so clearly it is not a rendering issue as the draw calls/tris are quite low. However, as you move around the world, the spikes seem to occur at frequent intervals - in some cases every few seconds, and in the profiler they come up ~100ms in Terrain.Data.BuildPatchMesh, which is awful. Note: I have tested all of this with standalone builds to remove that as a potential variable as well (still occurs). I have played around with all of the settings I can think of (while maintaining a similar grass density), and nothing mitigates it to any major degree (and I wouldn't expect it to as the cost likely scales against the density rather than the patch sizes). So the question is - am I missing something? Is no one else seeing this?