PHYS 123 Introduction

Hammering a stake into another's chest seems to not be as effective as shown on TV.

3 basic types of animation:

1. Traditional
2. Stop Motion
3. Computer

Compositing - Combining two or more separate images into a frame of a film.

Rotoscoping - A process in which a scene is filmed and animators trace the images. It is very noticeable and so it is used sparingly.

Motion capture - A scene is acted out, creating data from the sensor points which is then used in creative computer graphics images.

To create realistic animations, animators need to understand the principles of mechanic.

Chris Webster lists 

four levels of animated motion:

• Activity
• Arbitrary motion without the constraint of physical laws.
• Action
• Objects move according to physical laws.
• Animation
• Follows physical laws and is also intentional.
• Acting
• Intentional motion that conveys personality.

FALLING

Essential elements of animation:

• Timing
• Spacing

Norman McLaren
"It's not important what goes on each frame of film; it's the spaces between the frames that are important."
Basic principles for animation

1. Squash and stretch
2. Timing
3. Anticipation
4. Staging
5. Follow through and overlapping action
6. Straight ahead and pose-to-pose action
7. Slow in/out
8. Arcs
9. Exaggeration
10. Secondary action
11. Appeal

Frame Per Second (FPS)

15 FPS - Phone, Not useful for class.
24 FPS - Film
30 FPS - Video

Animators should use live reference for speed because Wile Coyote is suppose to be moving fast but the rate at which the backgroud passes him suggests that he only moves at 20 MPH.

The middle position is not the middle pose.

The "Odd" Rule

Distance between keys increases in the ratios 1:3:5:7:9... starting from the apex drawing.

Straight ahead animation is expressive but it can be hard to plan the scene or go back and adjust timing. Usually used in stop motion.

Pose to pose animation is less spontaneous but easier to plan. Common in computer animation.

Perception of motion is not the persistence of vision

In time, the middle key (3) is halfway between the first (1) and last (5).
In space, it is a fourth of the way down.
This rule applies to any key halfway in time from the point of release

If the spacings near the apex isn't quite right then the ball reverses direction at the top in an unnatural way.

The overlapping of an object from one frame to the next helps maintain the perception of motion.

If the action is too fast, the perception of motion can be lost because the object seem to disappear and reappear.

The brain has a discrete framerate

Wagon Wheel Illusion
A wheel seems to spin backwards because our perception of motion is confused due to strobing.

See Nyquist effect.

Stretch is a way of reducing possible strobing by minimizing the spacing between positions. Have to be careful that a character's features aren't distorted beyond recognition though.

Objects do not physically stretch as they fall, not even raindrops. They visually stretch due to motion blur. They actually flatten.

A slinky falls compressed and is weightless. Air resistance stops free fall.

Stretch in falling is not realistic. Stretch due to the law of inertia (drag) is.

Smear animation.

Odd rule can be used in falls viewed from above.

Falling away is less impressive than falling toward.

PATH OF ACTION

 

Line of action indicates the visual flow of action in a single drawing.

Path of action indicates the trajectory for a sequence of drawings in an animation.

Secondary motions also have paths of action such as a character's hand, arm, foot.

When gravity is the only force, the path of action is a parabolic arc.

A ball rolling off a table combines horizontal (constant) and vertical (odd rule) motion.

A ball dropped and a ball fired from the same height reaches the ground at the same time.

Two balls thrown from the same location at different angles that reach the same height will hit the ground at the same time.