UGO talked to Alan McFarland (Iron Man, Spider-Man 2, Spider-Man), who was responsible for the special lighting effects for Dr. Manhattan in Zack Snyder’s Watchmen. Here’s a quote from the interview:
Personally, I loved the scene where Dr. Manhattan is at the television station. Fans of the graphic novel will know what I’m talking about. From the standpoint of the most technically difficult scene to pull of with Dr. M, I recall it being in his laboratory when you see four of him. You see a glimpse of that in the trailer. We had to have Billy plus three other body doubles in identical mo-cap suits to pull that off, and it was very early in shooting Dr. Manhattan, so we were new to the process. It was a real trial-by-fire on that day.
You can read the full interview here.
Source: UGO