Mesh boolean Error

Hello Everyone
see the below image
When I boolean difference in mesh…
it does not work…
Anyone know the reason?

and then here is the rhino3d file

complex geometry in rhino sucks for mesh-nurb conversion but I have a feeling these orthogonal walls could produce nice results: nurbs from mesh, merge all faces, shrink trimmed surfaces.

then you can boolean for real.

Hi carpenter yoon,

There are interior meshes in your one joined mesh and I believe that self intersection is the reason the Boolean fails in this area. Run the command MeshRepair on the mesh and read the report on the first page. Then use Explode to explode the single joined mesh into it’s component meshes to see the problem spots while selecting the different parts. What was the original program used to make this mesh? There may be a workflow change needed there to prevent these interior meshes. A quick fix is to move the mesh box 2 units in the Y axis and then you avoid some of the interior mesh verts and the MeshBooleanDifference works.