IMD 4003: Character Animation I

For IMD 4003: Computer Animation, taught by Chris Joslin

Contents

1. 1. Character Design
   1. 1.1 Two Types of Character Styles
   2. 1.2 Creating Stylized Characters
2. 2. Modeling Characters
   1. 2.1 Surface Considerations
   2. 2.2 Skeletal Considerations

1. Character Design

• Artistic Considerations: When designing characters, we define the physical characteristics to match the personality. Physical characteristics include: size, proportion, shape, colour, texture and clothing. Poses and movement help define the individuality of the character but that is discussed in another lecture. After the physical characteristics are defined, we create sketches.
• Technical Considerations: While creating the sketches, you must consider time and budget. For example, if your character has long flowing hair, you might be better off to change it to short, not flowing hair in order to save time and money - any modeling and animation with hair and cloth can be complicated and expensive.

1.1 Two Types of Character Styles

1. Realistic Characters: These types of characters are used in live action films. They are significantly harder to animate because they must look realistic.
2. Stylized Characters: These characters don't necessarily need to be true to real-life forms - as long as the general idea is expressed. One important thing is that you must define the rules and constraints of the character (in what they can do to interact with their environment) and you must stick to these rules!

1.2 Creating Stylized Characters

• Body and Head: Stylized characters have a disproportionate head:body ratio. The head tends to be large in comparison with the body.
• Face: The face should be large enough to clearly see the emotions expressed.
• Eyes: Eyes convey a lot of emotion. Their size is important - large eyes tend to convey youthfulness and attractiveness (Psychology insert: women with large eyes tend to be perceived as open and beautiful) while small eyes tend to convey evilness (Psychology insert: small eyes tend to make people seem less open and less attractive). Eyelids help convey emotions as well - mid-way closed eyelids can convey tiredness. The shape of the eyes makes a difference as well.
  Finally, giving non-human forms human-like eyes can help give the character more human characteristics - it is easier to convey emotions and the audience will feel more of a connection to the character.
• Eyebrows: These convey a variety of emotions (think of your own emotions for examples).
• Mouths: Mouths are used for speech and emotion. The size of the mouth can convey different personality types: small mouths can mean the character is quiet (less speech) and less expressive; large mouths can mean the character is loud and very expressive.
• Hands: Because hands are naturally complicated, it is useful to simplify their shape and their movements when possible. Animating the general movement of the hands can be enough to convey the correct meaning (Ex. Small hand movements over a shoe would mean that the character is tying their shoes.)
• Body Segments:
  • Single Mesh - a single mesh covers the entire body. We need to specify how all the body parts will deform during animation.
  • Segmented Parts - you can segment the body parts at the joints (or where appropriate). This means you worry less about deformation but you need good techniques to hide the seams between segments.

2. Modeling Characters

There are two types of characters: Organic and Non-Organic. Organic characters tend to be smooth (Ex. humans and animals) whereas Non-organic characters can be smooth or hard (Ex. robots and frying pans). We'll look at the surface and skeletal considerations for both types of characters.

2.1 Surface Considerations

NURBs vs. Polygons vs. Subdivision Surfaces

NURBs are slightly more difficult to use because we use NURB patches to control the mesh. The advantage is that achieving a smooth form is very easy. NURBs are often used for faces but we may want to revert to polygons in order to get the proper jaw movement.

Polygons are easy to use because we have great control over the vertices. We tend to use these for solid objects that don't necessarily need an extremely smooth surface.

Subdivision Surfaces use a polygonal mesh but have a NURBs-like smoothing technique for a higher resolution appearance. These are very useful because we can attach a rig to the low-polygonal model to control the high resolution mesh without applying all of the weighting.

2.2 Skeletal Considerations

• Knees and Elbows: These are the easiest to rig and animate because they are hinge joints (rotate on one-axis). The skin motion is easy to understand: as the angle becomes smaller, the inside of the joint compresses and the outside expands.
• Wrists: More complex than knees and elbows - they can be rotated on 2 axes.
• Hips: Hips provide the legs with 2 axes of rotation (forward/backward and side).
• Shoulders: Shoulders are very complex because they do not rotate around a pivot - they rotate based on different bone combinations. The key issue is that we need to know how the mesh will compress with different movements. To solve this, we can use different models for different movements.
• Spine: The spine rotates on 3 axes but we deal mostly with the motion of leaning forward and back. We must have enough detail in the mesh around the spine in order for it to bend smoothly.
• Faces: It is composed of 2 major bones: the skull and the jaw. The jaw movement affects only the bottom part of the face. There are many muscles on the face controlling different areas. I will not list them because this isn't a biology class.