I'm seeing some subtle seams in auto-connected terrain with imported heightmaps. I've taken care to make sure the overlapping edges of each heightmap matches it's neighbors identically, and did hex dumps/diffs of the edges to confirm they match exactly. In the 2018.3.0b4 release notes there are two issues related to auto connect and seams between terrains: Terrain: Fixed issue where smoothing along terrain seams would create lines/creases along the seam. (1061923) Terrain: Fixed terrain auto connect However, the seams I'm seeing still appear in 2018.3.0b4. I've filed a bug report (1087844). Here you can see a subtle edge in the terrain. It's pretty hard to see in a static image, but when you are moving around the scene it is more obvious. This image shows where the edges of the terrain are (I've moved the terrain to make it clear).