Friday, November 1, 2013

Enemy Animations

This handsome devil is the textured version of the test enemy you may have seen in the game demo currently featured in "latest experiments." I wanted to post him here and talk about some of the interesting technical hurdles he presented. As you can see, he has three stages, starting out as a bomb-like object which will eventually fall from the sky in-game to deploy. The "closed state" of his eyes, eyebrows, and hat brim are simply textured on, that way I don't have to cut sockets into the geometry. When he opens up, the extended parts which are concealed in his head will simply obscure their flat counterparts.

The face and hat components extend using a single joint, the various components are simply weighted differently to extend to different lengths. Four other joints control his flaps and hatches, one for the radial leg hatches, two for the front and side hatches, and one for his tail flap.

For his arms and legs, I wanted to use only hinge or pin joints instead of ball-and-socket joints, to make him look especially rickety. I rigged up a special system using aim constraints to automatically orient the extra hinge components; each leg uses only four skeletal objects, so essentially I'm only using the joints which would normally be used for knees and toes. The leg springs are just alpha channel trickery on 8-sided cylinders, and use no extra joints.
He's essentially designed around old nutcracker soldier toys (because they are truly terrifying), so his jaw is mounted on a single axle with his coat tails, which bobs and swings as he moves around. I had the idea of making him fold up into a bomb while sketching out some simplified body shapes, and for the final design I included reference from old military aircraft panels. I gave him a cannon and wooden mallet hands to keep him looking primitive, and will eventually add smoke particles billowing from his head like a train.

Once I had built a rig to accommodate the stretchy pistons and swiveling pin-joints that replace his elbows and knees, and the mechanisms required to fold him up and deploy him, the animation process was pretty straightforward. Unlike Boot Hat, this guy only needed one walking animation to get around, so technical considerations were pretty light.

I tried to make him, jerky, mechanical, and clumsy; here you can see his arms stick at the apex of their swing like a wind-up-toy, and oscillate at a constant speed without easing in or out; both of which are big animation faux pas.

To give him a little more character, I added a precarious swaying motion and and had him fling his springy feet around to keep himself upright; aiming for comical, yet menacing. I'm particularly pleased with the way his jaw just swings and chomps loosely on its axle.

On top of everything I added a constant shuddering vibration, like he's about to shake himself to pieces. This is inspired by the clockwork contraptions in "The Great Mouse Detective", which frightened me as a child.

The attack animations are both based around a huge, dramatic wind-up, a great deal of mechanical rumbling, then a sudden, reeling reaction that almost knocks him down. Most of this guy's animations center around him almost falling over.

In these animations you can see the pin joints working overtime to keep him stable, and the menacing rumble that serves as his idle animation is more prominent.

The controls for his arms and legs are very simple, the joint orientation is all automated, and simple enough that it doesn't break easily.

The cannon fire requires a huge plume of black smoke for full comedic effect.

This animation is a strong contender for the most fun I've had doing an animation, partially because it served as a wonderful field test for all the strange rigging work I'd done, partially because it's so ridiculous.

I particularly enjoy how the animation starts off like some sort of awkward bird hatching from an egg, and ends dramatically, deploying his eyes last.
With an entrance like that, his exit had to be something special; so nutcracker dies how he lived, suddenly, violently, and dramatically. Initially I planned to have him fall apart or fly to pieces, but instead I decided to have him retract into his shell. Eventually, I plan to have the bomb give one last violent shake, and explode.

In this angle you can see how his hip hatches work; they open to let his legs in or out then close again, and there's slot that fits around the top pins of his legs.

And that, as they say, is that. I hope it was entertaining, if not actually educational. The current version of the nutcracker can be seen in-game by clicking the "latest experiments" button at the top of the page, though there are a few visual errors I'm still sorting out.


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