Knowing what you can and can't do realistically is something that not all directors are able to grasp, and Blomkamp utilizes his VFX experience exceptionally well (and even did a quick 3D model of the Moose robot). The character of Chappie is played by Sharlto Copley, and not only did he do the voice acting, but he was on set every day physically playing the character, which meant he had to be painted out of every frame and replaced by the 3D model — which took quite a bit of effort considering how the film was shot. A new VFX reel from Image Engine shows just how much work it took to transform Copley into the intelligent robot:

In this video, Mike Seymour from fxguide breaks down some of the challenges that animators faced. He's also got a terrific accompanying article over on fxguide:

Creating Chappie Based on Real-World Parts

Image Engine has worked on all of Blomkamp's feature films, doing mostly character work, but for Elysium, they actually did the effects for the whole film. They specialize in character work, which is why the models in all of these films look so good and blend right in with real objects.

And from NAB this year, Lead Animator Earl Fast from Image Engine explained their work on the film, how they created the models for Chappie and Moose, and how he used software like Autodesk Maya and Shotgun:

The workflow for creating Chappie was pretty incredible, involving the animators taking inspiration from everyday parts, and including those in the model. Once they had built the model in software, it was then sent to 3D printers so that full-scale robots could be assembled and painted by Weta Workshop to be used in the film. It's an unusual process, and it meant that the real-life props had to match the software-created model, instead of the other way around. 

Another interesting bit of workflow information is how they handled damage and the different body states that Chappie goes through. Instead of creating them in software and then having the props people match those looks, they destroyed or roughed-up the physical models, and then matched those in software later with the help of high resolution images of the models.

Just some of the crazy stats on these models:

Certainly Blomkamp's shooting style made the VFX a bit more difficult later on, but this also added to the realism. By knowing the limits of his post team, Blomkamp was able to create a very realistic robot with the help of Image Engine and Weta. 

Here's a showreel to give you a sense of the amount of effects they did on the film, since Chappie was a digital creation for most of the film:

Behind the Scenes on Chappie

And for the hell of it, if you haven't seen it, the BTS footage from Chappie is pretty interesting, and it gives you a sense of where the VFX met the on-set practical effects:

Finally, the trailer: