How the Most Realistic Robot in Cinema History Was Made

By James O Malley on at

Entirely computer generated characters are now an established part of the Hollywood blockbuster. The likes of Guardians of the Galaxy’s Rocket and Groot are increasingly commonplace - just don’t mention Jar Jar Binks. Perhaps the high watermark for CGI success so far though (at least when you're talking about silver-screen robots) is Chappie, which came out earlier this year

The film told the story of Dev Patel’s Deon Wilson, an engineer at a South African weapons manufacturer, who figures out how to make the firm’s police robots think for themselves - just like a human. Unfortunately, the eponymous robot (played Andy Serkis-as-Gollum style by Sharlto Copley) ends up getting kidnapped and falls in with a bad crowd of gangsters. Worse still, the authorities decide that Chappie is a danger who must be stopped.

The thing that is really striking about the film is just how good the visual effects are, with CGI robot characters seamlessly blended in with the ‘real’ characters. So how was it done? To find out I had a chat with the film’s visual effects supervisor Chris Harvey, who explained the reason why blending in was so important to making the film work:

“Ultimately the goal of any visual effects is that it is blended seamlessly. My mandate with the team was really that was only step one with what we had to do. It's like he has to be 100 per cent believable, because as soon as he isn’t the whole point of Chappie - that he’s a character you’re supposed to connect with emotionally - [...] he’s supposed to register like any other character. As soon as we break any realism in terms of him blending, you’ll immediately lose that connection.”

It wasn’t easy to achieve though. To make Chappie work, Chris and his team joined the production early in development, much earlier than VFX would usually get involved.

3D Printed Robots

“Typically what will happen with visual effects is that someone will design it practically, build it and we will have to replicate it. And we’re going to be stuck with whatever decisions they made, whether that’s good or bad for us. Chappie was different because we actually came on very early and were part of that design process.”

According to Chris, Chappie was initially designed by the Weta Workshop, which came up with concept designs with director Neill Blomkamp. These designs were then given to the VFX team to put the design through its paces to make sure the robot can move similarly to how Copley will when he performed as Chappie, such as making sure joints line up and the physicality is correct. “It was really important to myself and Neil that there was no ‘cheating’ with the robot. Y’know he had to literally move - if we wanted him to move that way, we had to move him”, Chris said.

When it got to the set, Weta actually 3D printed three different Chappie models to use as a reference point. The models could be articulated but not animated - but were used to stand-in for the CGI model. For example, the team could film the static model under the same lighting conditions as the shoot to ensure that the lighting and textures on the CGI Chappie looked right in post-production. The 3D models of Chappie were apparently also useful as it meant that whenever Chappie or a police bot appeared on screen switched off, rather than animate in a still object, they could simply use the printed models. Brilliant.

It wasn’t just Chappie either that this was done with, the team also built a full scale version of Chappie’s huge rival Moose robot (imagine something like the Enforcement Droid 209 from RoboCop if you haven’t seen the film).

Building the CGI Robot

On the CGI side, making Chappie feel real was hard work. 22 different CGI models of Chappie were used throughout the film, all of which were subtly different to reflect changes (such as dirt and scuffs). Even the battery meter of his chest-plate had to be carefully tracked scene-by-scene to make sure it showed the right level - and in the edit, if shots were re-arranged, the battery had to be fixed to make sure it still made sense. All in all, Chappie was made up of a staggering 3,226,042 polygons, with 56,148 texture maps over 2740 object.

“We spent a lot of time really fine tuning that asset”, Chris said, “in the shaders, the textures and making sure the models are high resolution enough and making sure the models were high resolution enough and everything would hold up.”

Mapping Chappie on to the live action was a challenge too. “Typically on set and to get the lighting environment you’ll shoot like a HDRI” - basically a spherical background photo that CGI objects can be dropped on to, but that was too easy for Chris, who was keen to ensure Chappie was believable.

“What we would do is shoot multiple projections anywhere he moved - if we walked along, we would shoot all along his path of movement and then we would recreate the environments digitally, even though we didn’t have digital environments, we’d still recreate them digitally and re-project all those images back on to it, rather than just being spherical, because if he moved past a tree you felt the proximity of the tree in his reflection. [...] All of his lighting had true spacial awareness of him. Which was a big thing we really pushed and I think it really helped. It’s very subtle, but it helped with grounding him.”

Human Interaction

The other key thing to selling Chappie was direct interaction with humans, “[What] I encouraged Neil to do a lot [of] was not to be afraid of interacting with Chappie. Like we really encouraged the cast to touch him and hold him and hug him - whatever - and encourage them to pick things up and interact with his environment because all of those things while challenging for us when we get into post[-production] doing the visual effects, just help with that subconscious believability that he’s there.”

To make interactions easier, Weta built a chest-plate that matched Chappie’s proportions, so that the cast could get a feel for where the robot was supposed to be. Similarly, when filming, Sharlto was on set, acting with the ‘real’ cast members, so there would still be a sense of physicality. “He was wearing a grey suit, and had a grey chest piece with a harness on but aside from that it was just [acting] as normal, he’s the guy, you’re wrestling with him - we just had to paint him away after which was a lot of work!”

Apparently one of the cast commented on set that such was the connection between Sharlto and his CGI alter-ego that it didn’t feel like working on a visual effects movie, and instead felt ‘natural’.

Look Into His Eyes

Given how important eyes are to nonverbal human communication, I asked Chris if much thought was given to Chappie’s eyes. Surprisingly, they were apparently a last minute addition by Blomkamp, who apparently thinks about the robot not just in terms of how it will connect with the audience, but also in terms of what is plausible for the character. In this case, it was the idea that if we really did have police robots, just as there would need to be a speaker and microphone (hence Chappie’s ‘mouth’), it would need eyes so that the person being communicated with has somewhere to look.

Chappie has what appears to be a relatively low-resolution LED array where his eyes should be - which show an image of two pupils. The original plan was apparently to have a larger screen that would display emoticons to indicate Chappie’s mood:

“At one point we actually thought we were going to do a lot more with his eyes, I think there’s only three times in the movie when we actually changed the icon of the eye. We had hundreds of different emoticons we could put on that screen but as we went through the animation process we realised we didn’t need them to tell a story like his. His physical performance we got from Sharlto and the little subtleties the animators were going to add on top of that - the ears and things like that actually conveyed enough of the emotion that we didn’t have to tell the audience what he was thinking with an emoticon. So Neil just paired it way down to just three moments to add an extra little punch to it.”

Ultimately, whilst Chappie did receive mixed reviews from film critics, on a technological level it is a resounding triumph; whilst obviously on an intellectual level you know that Chappie must be CGI, you still completely buy into the character and its story. If I was a traditional actor, given what virtual robots are capable of, I might start nervously looking over my shoulder.

Chappie is available now on Digital HD download and Blu-ray, and on DVD from Monday 13th