Dramatic Interpretation can be an odd event with eye contact.
Supporting characters often are given a focal point that is to the left or right of center in order to add distinction.
Due to the use of focal points, supporting roles may not always be facing a majority of an audience (though, you do want to keep yourself angled towards the audience; use 45 degree angles).
Nor do they really break the 4th wall.
There is no need for supporting roles to speak to an audience because they are speaking towards another character.
Thus, supporting characters do not offer the eye contact to connect to your crowd.
Where Dramatic Interpretation does find eye contact is with the narrator.
Most DIs have a narrator character that does interact with supporting roles but also with the round's spectators.
Many piece selections either are written with or are cut to offer monologues for the narrator/lead.
Because monologues are not delivered to another character the performer can address the audience without looking awkward--no, "who are they talking to" moment.
Therefore, the narrator is really the only character that can truly interact with the audience.
You can not waste this opportunity to draw in those watching.
Scan the room to make sure all onlookers feel engaged.
Scanning also adds variation to your performance as roles with focal points only look at one spot.
Also, take the time to connect with members of the crowd.
Eye contact is a powerful force that intensifies a performance and helps people connect to your narrator.
Obviously with eye contact and scanning you do not want to over-do-it.
Keep it natural and controlled.
But if you do make an effort to really interact with your audience they will transcend from mere observers to participants in an emotional journey.