When you hear the words “CGI” or “3-D animation,” complex computer languages probably come to mind.

But when HBO tasked Pixomondo, the visual effects company that it works with on “Game of Thrones,” with designing the show’s dragons, it required something far more accessible and considerably cheaper: a chicken from a nearby grocery store.

“I was looking for an animal so we can really discover how the muscles underneath should work,” said Sven Martin, Pixomondo’s visual effects supervisor. “I called over all the animators and they all had to just play with the chicken … You could feel how the muscles underneath are moving and what are the restrictions, where the bone can’t go. We built our dragon basically the same way.”

Of course, creating the visual effects for “Game of Thrones” requires far more than poultry. Martin and his team use a variety of clay modeling software such as ZBrush, to design dragons that align with the show’s broader aesthetic sensibilities.

As you might imagine, the process involves frequent communication between the show runners and Pixomondo. The production team will send over a few concept paintings, and Martin’s team will work off those initial ideas to create 2-D models.

“It takes some effort to build it in 3-D, so the first approach is always very classical just to find out okay will there be new features, how much new detail we might see in the season,” Martin told The Post.

Once filming starts, there are still tweaks that need to be made.

“During these first animations we discover some issues, where we have to change the model here or there, or recognize maybe we have to add some more details as certain camera angles we might be really close,” Martin said. 

Although “Game of Thrones” falls under the category of fantasy drama, its world is designed to feel realistic.

“They are not shooting with lots of green screen,” Martin said. “They are really going outside on location and shooting in the real wilderness, shooting in real cities, so everything feels very real. This is what we wanted to transport into the creatures.”

The dragons had to be as believable as possible. “This was always our main approach, to not make the dragons too fantastical and too design-driven,” Martin explained. “The idea was always just to keep them grounded in reality, so the functionality of the body should be always visible and present.”

Martin and his team started working with the show after its first season. “If you compare the dragon models between season one and season two, it’s quite different,” Martin noted. “In season two they were more like chickens, standing around just doing little steps and in season three they were learning to fly for the first time so this had quite an impact on the design.”

This required some physiological tweaks. “Of course, the season two dragons, the relationship was not quite right,” Martin explained. “The body was too big, the chest was not really sculpted to carry on the muscles in the breast, which are needed to make it a flying creature.”

As the dragons grew, Martin’s team looked at other animals for inspiration, including perhaps the most iconic dinosaur from “Jurassic Park.” (Sorry, Newman.)

“The dragons had to become a little bit more aggressive overall, a little bit more like guard dogs, so it was important that they have a big difference between their demure pose when they’re just calm near [Daenerys], but very aggressive with a big showoff when there was someone attacking their mother,” Martin said. “The threatening pose was something we wanted to show a lot.”

From the onset, Pixomondo has kept a team of 22 to 30 people who focus solely on Daenerys Targaryen’s dragons, with the average production time per season ranging between 20 and 22 weeks. Season five premieres April 12.