Godot Version
4.2.2
Question
How to remove the upper part of the navigation region? I have attach an image. I have marked the part with red arrow.
You can just block it with some small, invisible collision shapes that occupy the voxels but are too small to stand on.
If you are on Godot 4.3beta6 or newer you can use the newer NavigationObstacle3D shape to discard unwanted navmesh sections.
If you world is mostly flat you can also use the baking AABB on the NavigatioMesh to define the bounds to bake. That will also make the baking faster because it can stop creating so many y-axis voxel layers for mostly empty space.
NavigationObstacle3D is also available in 4.2. But I manage to sort it out. Thanks for the reply.
The NavigationObstacle3D node yes but the discard feature is only available in Godot 4.3beta.
Ok. Once it will be available for download, I will try it. For now, changing the regions size removed those upper parts of the region. Thank you for your reply.