## Question of the Week

Principles of Animation - Page 3
by Danielthelion  |  23 November 2005

We are nearing the end of this tutorial! In the previous page, you created the keyframes that will adjust our animation. Let's pick up from there.

Some of you may be wondering, "why not just use motion tweening? After all, its a lot faster isn't it?" Faster, yes, but for really great character animation, or for maximum control, key framing it the way to go. So, how do we know where and when to place our ball? Well, on frame 1 the ball is up, assuming we want to make a cycle, we would place the down position in the middle and then end where we began...correct? Well, good enough for right now, so lets find the middle. Let's see, half way between 24 is 12 right...."but , but Daniel!" you say, " there isn't a keyframe on frame 12! Frame 12 is still part of keyframe 11!" Ok, poindexter, so lets put it on frame 13, no need to get all worked up. Animation, after all, is about life, and life doesn't always add up, so we roll with it...

We go to frame 13, select our ball, and then, the way I like to work, is I usually hold shift down and use the arrow keys to bring the ball down to the ground plane. We want to get that ball touching the ground, so don't be afraid to zoom right into that bad boy. Frame 13 should look something like this:

[ on frame 13, ensure the ball hits the line ]

Now we connect the dots. We go back and forth between frame 1 and frame 13 and we figure out where to put the 5 drawings we have that will give us the best "feel". To do this we ask ourselves what we know about the world around us. What affecting the ball? Gravity and the ground. How does gravity affect the ball? Well, as the ball drops it is going to pick up speed. What does this mean for our animation? This means that our drawings are going to be spaced differently in relation to one another.

So as the ball is just beginning to drop we'll place the drawings closer together so the action happens slower. As the ball begins to get pulled down by gravity, we place the drawings further apart. This creates the illusion that the ball is moving "faster". Spacing is a somewhat complicated concept to grasp and requires a significant amount of contemplation to really grasp. I encourage anyone truly interested in character animation to really think about the differences between Timing and Spacing.

Select frame 3, your 2nd keyframe. Now, to view the spacing of your keyframes, we use the onionskin option. This can be turned on by clicking the small button on the bottom of your timeline that looks like 2 overlapping squares. There's actually 3 buttons that look like this. We're using the one that's furthest left. Click it and you'll see 2 draggable "handlebars" that appear on your timeline. These represent the scope of your onionskin. Since we only want to see how our current drawing relates to our first drawing, we drag the left handlebar all the way to the left and we make sure the right handlebar is directly over our current frame. In case your lost, make your screen look like mine:

[ the onionskin button ]

If you select the ball and begin moving it around you'll notice that you can see not only it's present location but a ghosted image of the previous drawing. That's what our onionskin does for us. Lets put it to good use. Assuming our ball on keyframe two is currently in the same exact position as keyframe one, we use our arrow keys to begin nudging it down. My 2nd keyframe looked like this:

[ viewing frames with onionskin enabled ]

So in my mind, I am imagining gravity is starting to work it's magic on our ball. For our 3rd keyframe we're going to move our ball significantly further from its starting point. When you select your 3rd keyframe you'll have to make sure to re-drag the left handle of the onionskin so that it's over the first keyframe. This allows you to see the 1st AND 2nd drawings along with the 3rd. Shoot for something like this:

[ notice the three keyframes of positions visible ]

We continue in this fashion with the next 3 keyframes, gradually increasing the spacing as gravity takes hold of the ball. By frame 11 this is what I have:

[ a static preview of your animation ]

The next keyframe is the point of contact for the ball and the ground. For the most part, our sequence is complete. To make it a cycle, we need only to work backwards. To do this, we use a process of simply copying our 1st set of keyframes in reverse. Stay with me here. If you think about it, it makes perfect sense. Our ball makes contact with the ground on frame 13. On frame 15 we copy and paste the keyframe from frame 11. On frame 17 we copy and paste the keyframe from frame 9. On frame19 we copy and paste the keyframe from frame 7. On frame 21 we copy and paste the keyframe from frame 5. On frame 23 we copy and paste the keyframe from frame 3. Once the playhead reaches that last keyframe it loop back to frame 1 to complete the cycle. Its kind of like a yo-yo.