private static MeshCollisionShape createSingleMeshShape(Geometry geom, Spatial parent) {
        Mesh mesh = geom.getMesh();
        Transform trans = getTransform(geom, parent);
        if (mesh != null && mesh.getMode() == Mesh.Mode.Triangles) {
            MeshCollisionShape mColl = new MeshCollisionShape(mesh);
            mColl.setScale(trans.getScale());
            return mColl;
        } else {
            return null;
        }
    }
This type of collision shape is mesh-accurate and meant for immovable
"world objects". Examples include terrain, houses or whole shooter
levels.
<p>
Objects with "mesh" type collision shape will not collide with each
other.
jme3-jbullet/src/main/java/com/jme3/bullet/util/CollisionShapeFactory.java