In this example I have chosen to animate a little toy truck. Many people who animate for the first time often move the object too far, as they think in terms of the beginning and end rather than the process of getting there. To see an example, place the truck at the left-hand side of the screen and take your first picture. After you have shot this frame, move the truck to the far right side of the frame. Without taking a picture, press down on the space bar of your keypad. When you toggle back and forth, Stop Motion Pro enables you to see a rough two-frame animation, much like an animator who uses drawings examines his or her animation by flipping back and forth between the pages. You will notice that when the subject is displaced too far from the first position, the viewer gets the impression that the subject has disappeared and then reappeared in a different place. This popping off and on covers too much distance to be considered a “movement.” Keep moving the toy back toward its original position while toggling the space bar. You will eventually reach a point (especially if the image of one overlaps the image of the other) that you will get a sense that the truck has moved by itself. My general rule of thumb is to move the subject to a point where there is some overlap or at least to the point where the first image left off. If you go any farther than this, it would be best to introduce some kind of blur to justify a move of that distance in the span of one frame.
Figure 3.10 This move is good, as there is an overlap between the position of truck 1 and 2. The eye will blend these positions together and create the illusion of movement.
Now to create our first linear animation, we will need a guide. Remember the ruler that you used to frame the shot? Place the end of that ruler so that it lines up with the front of the toy truck on the first frame you photographed. After you have placed the ruler, make light pencil marks on the table showing where you placed the corners of your ruler. This will allow us to use the ruler as a guide and bring it in and out as we animate. Once you have marked and placed the ruler, push the truck so that its front aligns with the 1-inch mark on the ruler. We will animate the truck moving 12 inches in 12 frames. Once you
have moved the truck, remove the ruler and take a picture. Replace the ruler using the guide marks on the table and move the truck forward another inch. Remove the ruler and take a picture. Repeat this process until you have moved to the end of the ruler.
Now play back the animation, and you will see that the truck moves across the table and your ruler guide is never visible. Because we used even increments (1-inch moves), we call this a linear move. This is the simplest form of animation, but we can make it a lot better by making use of the process of ease in and ease out.
Ease in and Ease Out
English physicist Sir Isaac Newton described three laws of inertia. The first of those laws is of primary impor- tance to animators and is often paraphrased by the statement “An object at rest tends to stay at rest unless a force is acted upon it and an object in motion tends to stay in motion unless a force is acted upon it.” Inertia, by the way, is defined as the resistance of an object to change its state of motion (either moving or not). What this means for an animator is that matter never starts moving or stopping at a constant speed. Car manu- facturers always brag that a particular model goes from 0 to 60 miles per hour in so many seconds. It takes a while for the car to accelerate or speed up to get to 60 miles per hour. It never starts at 60 miles per hour. Conversely, unless the car hits a brick wall, it never stops instantly. The car and everything else for that matter slows down. So everything we animate will look far more natural if we speed it up and slow it down or ease in and ease out. Eases are typically worked out on the fly in the mind of the animator.
To make the process clearer, I’ll illustrate a way of creating an ease using simple math and geometry. First, place the ruler on a large piece of poster board and draw a straight line along its length. Using a compass with its point in the middle of the ruler (6 inches), draw an arc. Using a flexible ruler, measure the length of this arc. You should get something close to 18.87 inches. Because our move will take 1 second, divide the length of the arc by our frame rate of 12 fps; you will obtain 18.87 divided by 12 = 1.57 inches, or roughly Figure 3.11 In between animation frames, you can put in a ruler to use as a guide.
11
2 inches. Set your compass to 1.5 inches, and start dividing your arc into 12 segments. Once you have
done this, set your ruler along the straight line and line it up with the hash marks you have drawn on your arc. Then make marks along your 12-inch line. As you proceed along the arc division by division, you will see that the marks along your straight line become more widely spaced apart. The first increment will be small and get gradually larger until we get past the midpoint and the progression reverses. Using this method, we have created by graphic means an ease in and ease out.
For those of you who are fond of mathematics, a precise way of finding the increment is to solve the circumference by multiplying the diameter times pi (π), or 3.14. So if the diameter of your arc were the length of the move, 12 inches, you would multiply 12 × 3.14 = 37.68 to get the full circumference of the circle. Our arc is half of this circle. To obtain the length of the arc, divide the circumference by 2: 37.68 ÷ 2 = 18.64. You then divide the length of the arc 18.64 by the length of the move to get the increments: 18.64 ÷ 12 = 1.57.
Figure 3.12 Draw an arc above your 12-inch travel distance.