In order to achieve the seemingly simple shapes and look of the characters, there was quite a bit of custom rigging, and the characters had to be modelled to work from the right angles. Below is the basic Martin rig with the shapes panel. There was also a keying synoptic to help key quickly and easily.
Please click on the image to see it in full.
We began with the idea that character’s heads would always been seen side on, so started modelling a head that had a set of eyes on both sides, and that we could just rotate round when facing the opposite direction. However, as the storyboard progressed, it became obvious that we would need heads that could be seen from a 3/4 angle as well. As you can see from the image below the main head looks pretty rubbish from straight on. The two heads below that are each of the 3/4 angles. The main control panel had an option to switch the visibility of the heads so we could swap them out and the shape controls were attached to each head so that expressions would match. Using Softimage’s GATOR function was invauable in tansferring shapes to the other heads.
Here’s a test of a head turn to check that it would work ok and not distract the eye too much. An example in the film itself is when grandpa is holding open the door for granny, the head swaps from one 3/4 to the other 3/4. It was always our aim to make the transitions as un-noticable as possible.
The expressions of the character are fairly simple, modelled to imitate the feeling of plasticine being pushed around, so for example the eye sockets themselves being pulled up was an intentional device. We tried to make the shapes feel part of the whole head, and not an isolated section.
With Martin, his moustache was also a good way to help sell emotions. We tried a few different methods to make this work, but ended up going with geometry instanced on hairs, to match the style of his arms and legs, and allow some control over how smooth/messy it is.
The bodies of the characters are, as with the heads, designed to look simple, with a bit more going on under the hood to get graphically pleasing shapes. The main body was shaped with 3 controllers (the pink rings) but there was a second layer of controls which we could enable, in order to shape the cloth/silhouette. Given the way that the head turned, we thought it would be a good idea to be able to rotate the body independently of the shape itself, which you can see in the images to the right – the same rig position, but with the body rotate control round to the character’s left.
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The arms and legs were relatively simple, as we knew that they would be a constant colour. They are controlled with a stretchy IK chain overall, and then are shaped using clusters on the curves of the arm.