Moviegoers now take for granted a steady improvement in computer- generated imagery - but you know you are seeing something special when a CGI effect makes a room full of entertainment reporters gasp.

This is what happened when The Straits Times and other press were shown breathtaking 3D footage from the new film The Jungle Book, in a presentation in Los Angeles by director Jon Favreau and special effects supervisor Rob Legato.

The movie, a remake of Disney's 1967 animated musical comedy of the same name - itself based on Rudyard Kipling's beloved 19th- century stories about Mowgli, a boy separated from his family and raised by wolves - showcases CGI creatures and a jungle environment so photo-realistic, they are often barely distinguishable from the real thing.

Recent leaps in this technology made a convert out of Favreau, a self-described Luddite who cut his teeth on effects-light films such as the 1995 indie comedy Swingers, before moving on to action-packed, CGI-heavy blockbusters such as the Iron Man franchise (2008, 2010).

Favreau, 49, says director Alfonso Cuaron's Oscar- winning space adventure Gravity (2013) opened his eyes to the possibilities of shooting digitally rather than on film and using motion capture- based CGI rather than adding effects in post- production, as was done with Iron Man.

Of Gravity, he says: "I was very impressed with it and I knew a lot of the people who worked on it. My kid saw it with me and he was, like, 'How did they do that?'

"And I said, 'I'll find out'. I usually know. I'll say, 'That's green screen, that's CG, that's forced perspective'. But I was at a loss with that film."

This paved the way for Favreau to agree to direct the new animated adaptation of The Jungle Book, which is now showing in Singapore cinemas, and borrows techniques from other groundbreaking visual- effects films, notably Avatar (2009), Life Of Pi (2012) and Rise Of The Planet Of The Apes (2011).

"If there was a giant we were standing on the shoulders of, it was Avatar. Avatar was the first time I got what this whole big-screen 3D format was about. I got why you had to go to the movies to see that. It was a great experience too.

"Since then, 3D has been a big piece of business for Hollywood, but I don't know if anyone has ever outdone the 3D that was done there. So we shot native 3D, using the system that James Cameron had been a part of developing, along with all of this technology that people haven't really been using," says Favreau.

He presented the footage using a newly designed Dolby 3D laser- projection system, which The Jungle Book will be the first film to be screened in at selected theatres around the world The system has not yet been installed in Singapore cinemas, according to Disney.

The result is a story where the only live-action character is Mowgli, played by 12-year-old newcomer Neel Sethi. All the animals and much of the environment were created using computer-generated and motion-capture techniques.

The effects have wowed critics.

According to Favreau, the incredibly detailed animation of the animals is so cutting-edge that the only thing comparable is what audiences saw in the Oscar-winning movie The Revenant, when a CGI bear attacks Leonardo DiCaprio's character.

The team researched animal behaviour and studied every talking-animal movie they could get their hands on.

Favreau says: "We never asked them to behave in a way they normally wouldn't. Dogs or wolves are very expressive with their eyebrows so you could get away with lots. Cats don't use their eyebrows. Bears use their lips and eyebrows. We never wanted to push it into an area where it got weird."

The look of many of the main animal characters was customised for the actors who voiced them in the star-studded cast, which features Ben Kingsley as Bagheera, the panther who looks after Mowgli; Bill Murray as Baloo, Mowgli's bear friend; Idris Elba as Shere Khan, a tiger who threatens the boy; Scarlett Johansson as Kaa the snake; and Christopher Walken as King Louie, a now-extinct species of ape known as a gigantopithecus.

"In the case of the snake, having Scarlett didn't affect the design. But for King Louie, we really wanted it to have Christopher Walken's blue eyes and the look and the way his face is rigged.

"With Bill Murray, we could take advantage of the way he uses his eyebrows. It was enough that you could see the soul of the actor, but not enough to take you out of the reality of the movie."

Still, when Favreau was initially approached about directing the remake, he did not think anyone could improve on the 1967 film, which left a deep impression on him as a child.

But Mr Alan Horn - chairman of Disney Studios, which has been updating several of its classics, including 1950's Cinderella (Cinderella, 2015) and 1959's Sleeping Beauty (Maleficent, 2014) - persuaded him that The Jungle Book was ripe for a retelling using the latest in CGI, to "really embrace this new technology and see what we can do if we push it to its limit".

Favreau still wanted to pay tribute to the original, which he says was special because it was magical, surreal and dream-like, and "considered a high-water mark among Disney aficionados because of the characters and the music. That's what I remember about it and what I wanted to preserve".

"You are serving many masters when you make a film like this. You are trying to honour the emotional memory of people who grew up with this stuff. But you are also trying to make a movie that appeals to the full audience."

The way the technology was deployed also suggests that CGI can be used not just to add "hard surfaces" such as the ones seen in action movies such as Iron Man, but also create a complex natural environment such as a jungle.

Favreau says: "I thought if we really set it up, could we do something that took it to the level where you were watching something that was either photo-real or pleasantly elegant, beautiful and hypnotic?"

For all the technical wizardry, however, the crucial thing was to have a human protagonist viewers could relate to, especially as Mowgli is in almost every scene.

Favreau says he was starting to worry when they had auditioned about 2,000 children across the world and still not found the right one. It was only when he saw Sethi, then a 10-year-old boy living in New York, that he knew they had the final piece of the puzzle, the young actor evoking the same impishness of the animated Mowgli from the 1967 film.

"When someone is on the screen for that much of the movie, you don't want someone you get tired of. You're going to need someone who holds the screen and is interesting to watch.

"You have to breathe life into this thing, otherwise it's just an exercise in technology. It needs to have a beating heart in there."

• The Jungle Books is showing in Singapore cinemas.