(In short, to draw two in-betweens to show a constant speed, draw the first in-between approximately 1/3 of the way in from the first keyframe, and then draw the second in-between halfway between the first in-between and the second keyframe). I was animating a walk-across for work one day, and I wanted to draw two in-betweens between two keyframes. Wanting them to be equidistant to show a constant speed, I knew that the first in-between should be closer to the first keyframe, and the second in-between should be closer to the second keyframe. I knew that the 50% mark should be a small gap between the two in-betweens. Here is a simple example (which is more like a slide-across): I had done a couple of walk-across animations for the same project, and I had done them in the same way: draw the first in-between about ¼ the distance from the first keyframe to the second keyframe; and then, draw the second in-between halfway between the first in-between and the second keyframe. It looked right to me, but as I was coming on this last walk-across, I began to question if what I was doing was accurate. So, on the side of that frame I drew a ruler and fractions to sort this out. The zero and one on the line segment represented the first and second keyframes, respectfully. I first thought that the first in-between, I 1, should be 1/4 of the way in. I hypothesized that the next in-between should be halfway between the first in-between and the second keyframe, so I needed to find the midpoint of the two values. Um…5/8 of the distance would be 3/8 off from the second keyframe, which doesn’t equate to the 1/4 off of the first keyframe. In order to make it a constant speed, I need the distance from Key 1 to I 1, I 1 to I 2, and I 2 to Key 2 to be 1/4. When I drew it out, it was clear why it wouldn’t work. Although they are both 1/4 off of each keyframe, the distance between the first in-between and the second in-between is too large (by 2/4). But I was sure I was doing it right! It turns out that I was, but I had to think of the in-betweens as thirds instead of fourths. It makes sense because there are two in-betweens to draw, not three (I guess I thought thinking in fourths because of four total drawings). When I decided to place the first in-between at 1/3, I came to this. The second in-between goes 2/3 of the entire length. Now the distances between the drawings are equal: 1/3 off of Key 1, 1/3 between I 1 and I 2, and 1/3 off from Key 2.
As for how my drawings were affected, they definitely followed this math. In order for me to emulate the frames in fourths, I would have marked the 50% point, then place I 1 halfway between Key 1 and the 50% point. Then I would have to mark halfway between the 50% point and Key 2 to place I 2—or, given the calculations, draw closer from that to Key 2. I knew that wasn’t close to what I was doing, so I wasn’t thinking that my drawings were right just because I changed the numbers representing them. |
ArtistDiamond Stewart is interested in animation, comic book art, video games, and music. Categories
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January 2024
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