hmmm..I’m not having any issues. It can take awhile with large terrain but not hours. That’s the part that gets me. Is your box pretty robust? I would be interested to hear what happens with tests on smaller terrain. Is there a ton of assets in the terrain? Sorry for all the questions but I want to try and duplicate what you have.
I understand for best performance, it’s ideal to keep the terrain at a moderate size when not creating things procedurally. This is suggested by Unity actually. What that optimal size should be, is really up to you based on the situation. With this in mind, it’s also not recommended to try and create a mesh for the entire terrain when it’s a big area. Creating small sections where your ai will be moving around is my suggestion as a best practice. For example, there is no need to create a mesh over the water or mountains or between great distances if the ai will never really travel there.
I might suggest trying a couple things:
1. Loading different scenes as you move through the world
2. Create a few different meshes, instead of one giant mesh, and use graph tags so your ai will go wherever his navigation graph tags match.
3. Don’t use Unity terrain and perhaps import your own mesh or create the terrain procedurally. (This of course is much more involved.)