So, when creating an AImesh, which is better to use Stairs or Ramps? Ramps can be a lot cleaner and easier to implement, It would seem to make sense that ramps would be easier bot to use as well. After all, ramps have a lot fewer faces, so they would be simpler and less likely to have any mesh issues.
However it turns out that the navmesh process works better with stairs than ramps. Ramp navmeshing is inconsistent. Stairs actually navmesh much more reliably. Steep stairs will also work, where a steep ramp might not.
A lot of times, the col2 can be cloned and cleaned up a little for the AImesh and it may have ramps. The col0 will have stairs, but it is usually more complicated overall than what is needed for the Aimesh. One way is to use the stairs from the col0.
To start, make a clone of col3 and then delete all the mesh except to the stairs. Clean up the stairs and then export to 3ds format. 3ds format is a generic format that keeps the size and position information, so it can be imported back into the scene and attached.
The following is a good example of a stair AImesh. There are not long thin baces and its' all closed up.
The photo below shows three different stairs that will be used to demonstrate different methods and how the situation may dictate how much work needs to be done.
Looking at this stair mesh closely the stairs are not properly attached to the sides. The sides can't just get deleted. They are needed to keep the bots from trying to get to the stairs from the sides and run into the side rails.
One solution would be to attach the sides to the stairs properly, by creating new faces to connect each step. If this was a stand alone stairway, that would be the best way as it will work in most configurations that is is used.
Another solution, since the the stairway is part of a building,and only the part of the sides is needed to block the bots trying to use the side of the stairs at ground level, but with the sides separate from the stairs.
This is a better picture of another stairway:
And this is a closeup showing how the side rails are seperate from the stairway: