Everything we do in creating and drawing our characters is based on simple 3D shapes, usually a sphere - and specifically, the head sphere. In drawing heads and faces, the formulae created for each character is geared around the sphere. The width of the eye is a fraction of the sphere's diameter, for example; the ears are so many fractions of the head in size; and so on.

One important distinction: the sphere is not a circle! The sphere represents a 3-dimensional object which can be tilted and rotated. The objects on the surface of that sphere - eyes, noses, ears, color separation lines - all move as the sphere moves. If you look at the head as a circle, you must guess where things belong... and many starting artists guess wrong. A sphere has volume, and for the type of drawings we do that's very important (which we'll explain in detail in a future chapter).

The head sphere is also used in determining the height and shape of the overall figure. A character is so many heads high, so many heads wide, and so on. The head size may change from character to character - and that too is a useful measurement, allowing us to determine exactly how big (or small) a character is in relation to other characters.

There is no single, 'correct' rule to determine a character's relative size. A great deal depends on the style of the specific project.

Part of working out a character's proportions is to work out their range of actions and expressions, to make sure the drawing matches the feel we have of the character. This is done by creating model sheets for each character. Creative playing around at this stage saves a lot of headaches later when we're trying to produce a finished product.

Different model sheets have different purposes. Some show sample actions and movements; some show off costume considerations. Some are simply construction diagrams: 'this character is this many heads tall...' and so on.

The stories we write and illustrate will (hopefully) be read by humans; so the characters have to display emotions and portray actions that can be understood by humans, both in facial expressions and in body langauage. Cartoon animals must have the same 'expression points' as humans: eyes, eyebrows, the folds (or lack of same) on the cheeks, and the shape of the mouth. Animal characters have a few extra readable attributes, and the most important of these is the set of the ears and the angle of the neck to the body.

The trick for us is to mimic human expression without losing the inherent 'animalness' that lies underneath. Some comic artists - notably those with a Japanese manga influence - simply draw a cartoon human face and add a small, animal-like nose or muzzle to it (plus ears poking through the hairline). We try to go the other way: portray the animal first and foremost, but with human-readable expressions. Anyone who has ever tried to figure out what a cat is thinking knows: this is not easy!

Finding the right combination of animal and human elements to suit a particular character is tricky, but fun. Just as human film and TV directors have casting calls for actors, we will sometimes sketch out lots of different versions of a character until we get the one we like for the part. Again, a little extra effort at this stage makes things a lot easier down the road.

As noted, character expression is a combination of human-readable facial expressions and body language. It's probable that real space aliens won't look like animals, nor will they use body language which humans would recognize; but we are not trying to push the boundaries of human understanding when it comes to alien psychology. We're telling simple (hopefully fun) stories that can be understood by humans - specifically, young and young-hearted humans - so our animal characters must act and react and perform in ways that are easily understood by humans.

Creating believable characters a reader can identify with involves a lot more than adding ears and a tail to a human: it's a matter of simplifying complex emotions so they can be understood at a glance, to make the characters seem real. If they're not real, no one will care about them, and the story will die.

As noted elsewhere, cartooning is primarily the art of leaving out details. Knowing which to leave out and which we must leave in is the key to all comic art - a subject we'll cover in another edition of Secrets.