Once you find solid reference, watch it over and over again to get a good feel for the motion of the body and the mechanics of lifting a heavy weight. We’ll move on now to the all-important gathering and analysis of reference. The ball in our example is very heavy, therefore the effort exerted by the Box Boy must be seen to be very great in order to convey that sense of weight. If every action has an equal and opposite reaction, then in order to move a heavy object, the force exerted on the object must be greater than the force exerted by that object. We also need to keep Newton’s Third Law of Motion very strongly in mind. So a successful animation meant to convey the lifting of a heavy weight will have to demonstrate an understanding of how the centre of gravity travels in order to be believable. As he lifts the ball though, the centre of gravity shifts but has to remain over his base of support otherwise in reality he’d fall flat on his box bottom. In this exercise, the ball’s centre of gravity will be its geometric centre, while the centre of gravity for our friend the Box Boy at the beginning of the animation when he’s standing upright will be around the height of his box belly button.
So the centre of gravity, as you’ll all remember from school, is the average position of weight distribution in an object or character. Just before we start though, I’ll be using Maya, but obviously the same techniques can easily be transferred to the 3D package of your choice. However, that’s simply the way I have approached the exercise, and it’s by no means the only way to skin this particular cat, so please find your own preferred way. Sorry to disappoint but we won’t be seeing too much of the Graph Editor this month as by the end of the animation I’ll have keyed in poses every 2-4 frames in order to help transitions from pose to pose and to add subtle detail, which the computer by itself cannot achieve. After that it’ll be time to block out the key poses. We’ll then – as ever – move on to the essential step of gathering and analysing good reference. So firstly we’ll consider the physics behind what we’re trying to achieve: we’ll look at the centre of gravity of an object and a character and see how the latter shifts during their interplay, and we’ll also revisit Newton’s Third Law of Motion, which states that every action has an equal and opposite reaction.
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