[Closed] Is Face Visible From Camera

Hy all, i am doing adaptive mesh script and have a huge problem:

Any ideas how to determine is face visible in camera frustrum? Vertex and edge tests are easy but what i am doing in that case? :

PLANE 4 vertex, Camera looking very close to the middle of the face, in that case all 4 vertexes and edges are invisible? Any suggestion how to fight that situation?

Thanks and sorry for shity english