Angular indication on the method publishCone

Hello, 

I wanted to ask a question about the angle value of the publishCone(...) method.  Does this value have to be specified in radians or angles? I used several values like PI, PI/4 and the angle of the cone always looked wrong.

How do I specify the angle so that my cone has an opening angle of 30° degrees as an example.

Many thanks for the great library :=)