Antenna Pattern

I'm attempting to create a couple of custom antenna patterns for our model and have a few questions on how it is implemented in RadioCompass. A quick talk with a coworker led me to believe that RC looks at the ERP and then the radio pattern is basically a multiplier (0 to 1) of that value. Is that the case?

Basically what we're doing is using a different software program to model an omni antenna that is physically mounted on a tower. It spits out an azimuth pattern that accounts for a few tower variables that we put in. It gives us gain information in dBd I think. Anyways, it can be scaled to be between 0 and 1 if need be.

The main question is, assuming the antenna pattern is indeed a multiplier, does it apply to the antenna gain value or the ERP?

Sorry if I'm not explaining myself fully.

-Josh