How do grass and stone brushes generate obstacle avoidance maps in the terrain?

I use Unity’s Terrain system and it works fine most of the time. But when I brushed the grass on the terrain, the resulting navmap became bumpy. I tried to change the Layer of the grass prefab to not participate in the generation, but after brushing on the terrain, the navigation map will still add it to the calculation. what should I do?

Hi

Are those marked as trees or grass in the terrain system? Grass shouldn’t be included, but trees and similar things are included.
If you have a prefab for your objects, you can exclude them by setting the layer (and adjusting the layer mask on the recast graph accordingly).

yes,those marked as trees or grass in the terrain system