Hi everyone
I have an issue with the boolean modifier or the bool tool.
I guess I’m doing something wrong here, but I can’t figure it out.
I have this terrain mesh:
And i have this wall:
And when trying to boolean, it doesn’t cut a hole, but added vertexes along the edge, as you can see in picture one.
What could be the issue here?
Now hide the wall… you may have the hole you seek.
haha, no… if it would be that easy, i wouldn’t ask this question here 
Can you post an image of the terrain mesh, AFTER the boolean operation, with the wall hidden? This may help with diagnosis.
the first image is actually the one after. It created additional vertexes along the edge, but didn’t cut it.
The shading of the mesh looks strange. Check the direction of the face.
Booleans are vey bad at non-manifold meshes…
Also: if the modifier is just added and not applied… then do not look at it in edit mode…
If your terrain is simply a deformed “plane”… maybe try adding a Solidify modifier before the Boolean modifier. Booleans are about Volumes, rather than points, so perhaps giving the terrain Volume will help.
the face direction looks accurate
it’s actually a mesh created from 3d points with delauney and subdived one time. The original triangulated mesh doesn’t work either.
But it doesn’t appear to have thickness, hence no volume, if I’m not mistaken. Try Solidify before Boolean.
I extruded it before. Solidify doesn’t work too well, because it extrudes along the normals and the mesh has quite a lot of them…
Vertices appear to overlap and tangle.
Unlock the tangled Vertices with Smooth Vertices and try it
thank you for your answer. The mesh you see is actually the mesh after the boolean. I guess i put the images in the wrong order, it’s seems to be confusing.
Cut only the part where you’re going to run the boolean and share it here. I’m not sure with the image. 
Oh wow, that’s awesome.
Here’s a download-link:
https://www.swisstransfer.com/d/ae54ec81-afe6-47da-978d-04cfa41034d8
Hehe… you was faster 
I was trying to select the “edge” by using one outer edge and then select similar and the extrude doenwards to get some “volumemetric” object… wheni dioscoverd:
overlapping geomtrey
manifold edges in a place you do not want them (possible problematic when boolean…)
and finally… normals…
…so yes just flip:
Oh, now i feel stupid^^
Thank you very much!
