Boolean region turns black after operation

[liamyongging]

Hi team,

im looking to boolean a plane(pink) with geometry ( blue ) 

Both basic editpoly geometry. 
however when i boolean my plane with the geometry, it results in a black region. Can Someoone explain to me how this happened.. Really appreciate this. 

[wernienst · Accepted solution]

Similar situation here: Boolean will create an additional coincindent polygon with reversed normals. See my reply to you other post.

[liamyongging]

I appreciat you Wernienst