Introduction to Motion

Submitted by sylvia.wong@up… on Wed, 06/09/2021 - 18:49

The definition of motion as per Britannica is:

“Motion, in physics, changes with time depending on the position or orientation of a body. Motion along a line or a curve is called translation. Motion that changes the orientation of a body is called rotation. In both cases, all points in the body have the same velocity (directed speed) and the same acceleration (time rate of change of velocity). The most general kind of motion combines both translation and rotation.”

Motion is what brings animation to life.

A great tip to master motion is to record yourself performing different movements and actions. Then recreate with your animated character.

There are techniques to using motion that will bring key elements of our characters to life. They follow.

Sub Topics

Timing and weight are a coupled pair. Why? Because to animate realistically, there is a timing to the weight of the character. For example, if you had a little mouse, you would create quick movements. For a more significant character like an elephant, their action would be slower and more of a thump. We want to believe that the character moved, not that someone moved the character.

To effectively show the weight of a character, pay attention to the ‘impact’. The impact shows how much effort it takes to stop the body weight from its downward motion, and the impact coming out describes how much effort is needed to raise the body weight.

Diagram of effect with gravity part 1
Diagram of effect against gravity part 1
Diagram of effect with gravity part 2
Diagram of effect against gravity part 2

Arcs are gestures or lines of action. Arcs are what give your animation consistency and flow.

If we think about anything in nature, nothing moves in mechanical-like lines. Arcs increase the beauty and natural way things can move. They are gestures or lines of action.

Below are examples of arcs in character animation.

Diagram of motion arcs

Follow through and overlapping is based on real-world physics.

Follow through:

  • When a character or object stops suddenly, loose parts keep moving
  • Shows material properties of an object or character
  • Required for an animation to look realistic
  • It can be exaggerated for a cartoon-like effect.

Overlapping action:

  • Timing of different parts should be different
  • Items down-chain from the main mass should move after the main mass
  • When a character or object starts moving, loose parts drag behind
  • Helps animation feel flowy and smooth instead of rigid or robotic.

So, for example, follow through in animation would appear when a character with a scarf is running. When they come to a complete halt, the scarf will continue to flow in front of them and then fall back where the character has stopped.

Overlapping is like follow through as they are closely related to achieving the same goal of realistic motion.

Overlapping action is the idea that different parts of the body or character will move at different rates. So for example, if you had an animal character and made them run, their legs will be moving at a different speed to their head.

Both overlapping action and follow through are ways to provide convincing motion to animation.

Dynamic physics-based simulation is a way to automate this process.

In this topic, we covered how motion brings animation to life.

We considered timing and weight as a coupled pair. To animate realistically, there is a timing to the weight of the character. To effectively show the weight of a character, pay attention to the ‘impact’. The impact shows how much effort it takes to stop the body weight from its downward motion, and the impact coming out describes how much effort is needed to raise the body weight.

Arcs are gestures or lines of action. Arcs are what give your animation consistency and flow. They reflect the way things natural move.

Follow through and overlapping are based on physics principles.

Follow through:

  • When a character or object stops suddenly, loose parts keep moving
  • Shows material properties of an object or character
  • Required for an animation to look realistic
  • It can be exaggerated for a cartoon-like effect.

Overlapping action:

  • Timing of different parts should be different
  • Items down-chain from the main mass should move after the main mass
  • When a character or object starts moving, loose parts drag behind
  • Helps animation feel flowy and smooth instead of rigid or robotic.

Additional resources

Here are some links to help you learn more about this topic.

It is expected that you should complete 12 hours (FT) or 6 hours (PT) of student-directed learning each week. These resources will make up part of your own student-directed learning hours.

Motion graphic examples

Character animation tutorials to watch: 

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