The couple were there to learn more about the work of Cinemagic – a charity that uses film, TV and digital technologies to inspire and educate young people.
It was the first public engagement on the second and final day of their visit to Northern Ireland.
They started Thursday with a private meeting with officers and staff from the Police Service of Northern Ireland at Hillsborough Castle, Co Down.
During the Ballymena walkabout, they spoke to members of the public who had been waiting a number of hours to catch a glimpse before heading inside the centre.
Wearing a Mulberry coat, Kate chatted to officials from Mid and East Antrim Council while William spoke to DUP MP Ian Paisley, who presented him with a wooden walking stick.
The couple then talked to Emma Noble and Jack Francis, who played them a short film they recently made.
They also watched young budding directors and producers as they practised shooting a film.
The Duke and Duchess chatted to the Cinemagic members as they demonstrated the software used to help create