Everything moves naturally in an arc. When your arms swing while walking. When a pencil falls off your desk. Even a speeding bullet.
Use the grease pencil tool to help guide your arcs.
Your object will slow in and slow out of each arc.
What is squash & stretch?
We use squash to show impact. See the bouncing ball below. The moment after it has made contact with the ground it squashes with impact before returning back up.
We use stretch to emulate motion blur. The faster something is moving the more we exaggerate the stretch. See the bouncing ball below. When the ball is at it's fastest is when it is stretched.
What is Timing & Spacing?
Timing is how long something take to happen. If all four of these spheres take 24 frames (or 1 second) then their timing is exactly the same.
Spacing gives the appearance of something moving faster or slower. If an object is placed closer to where your last keyframe was located then your object will move slower. If your spacing is much farther from the previous keyframe then your object will move faster.
What is Ease In & Ease Out?
Ease In is when your object starts out slower and eases into a quicker movement.
Ease Out is when your object starts out faster and then eases into a slower movement.