Realistic character motion is one of the most difficult things to model. By the time you’ve added facial expressions and speech to a virtual character’s repertoire you’ll be trying to manage tens or more likely hundreds of discrete keyframed points. You can handle these the hard way by plotting them all by hand, but computers are supposed to make life easier, and for character animation, that means Alias MotionBuilder.

MotionBuilder has been used in film and game design since version 1. When you’re looking at a game character running, walking, climbing or shooting, the chances are that the sequence of moves was put together in MotionBuilder. Motion theory is simple enough. Start by importing your character – and a character here can be anything from a humanoid model, some other creature, or even a collection of disconnected objects. Next, a Characterisation process defines how the different parts of the character connect to each other, producing a dependency tree that links kneebones to thighbones, and so on throughout. Without this step limbs fall off and go their own way during animation, which isn’t usually the desired effect.

Next, constraints are created which limit certain kinds of moves. So, for example, your character’s head won’t be able to move through its chest. Finally body parts are keyframed into movement sequences. These can be created as cycles, which can be ‘played’ in a game when a character walks or runs. They can also be interpolated from a set of poses, so you need only specify key points in the cycle and MotionBuilder will tween the steps between them. The Inverse Kinematics (IK) chains mean that if you move a hand, the rest of the arm will be moved into place automatically.

The features in MotionBuilder are dedicated to these different steps, and while related but much simpler versions of these tools are included in both Maya and 3D Studio, the MotionBuilder feature set is much richer and easier to work with. You can specify poses in a separate Pose editor, or you can use the main render window. There are also motion graphs that indicate the rotation, translation and scaling of a body part, and you can manipulate these directly. For the lazy – and make no mistake, creating realistic motion is both time consuming and difficult, even with all of the tools available here – MotionBuilder supports motion capture files in the main industry formats. There’s even a live monitoring option for watching capture as it happens.

What’s new?
For existing users, there’s a healthy crop of new features, although most of these are of the evolutionary rather than revolutionary sort. Undo is finally available for most actions. But some notable basics, including parts of the Characterisation and posing process, are still undo-free. Another minor change may confuse some, because simple IK constraint option has been removed. All IK constraints are chained now, which is a small distinction that more or less makes sense, but may cause some head scratching for anyone used to the older feature set. Multiple processors are now supported, assuming your hardware and OS can handle them, and there are some minor extras like the ability to make knees and arms bend backwards – useful for birds and cartoon characters, less useful for people – and to export scenes as JPEGs.

Tweaking rather than transformation is usual for an x.5 release, and bigger changes are apparently due in version 8 of the software, but this won’t be out for six months to a year.

MotionBuilder is clearly a niche product aimed at a niche market. If all you want to do is experiment with basic character animation then you’ll be better off with the much cheaper Poser or the free DAZStudio. The nearest direct competitor is Credo’s LifeForms which is around a quarter of the price and includes a suitably basic selection of tools. In terms of features, MotionBuilder wipes the ground with it, but for mid-level 3D animation on a budget, LifeForms is a reasonable alternative.

Otherwise MotionBuilder itself sits unchallenged at the head of the pack. It’s costly and time consuming to learn, but it’s also the product of choice for professional movie animators and game designers. If you work in those areas, you’ll want it. If you’re curious about how those areas work, you may want it too, just to see how the magic is put together. But it’s not for the timid or those looking for instant animated gratification, so make sure you’re up for the challenge before splashing out.