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At this point we have the character on the platform and moving. Obviously, there's nothing happening other than the platform and the character moving. Now the character is going to be affected by the motion of the platform. He is also going to be affected by gravity so let's go ahead and work on those forces. So the first thing we have is we have two forces. We have gravity, which is pulling this character down, and then we have the actual motion of the platform which is actually moving him right at the feet.
Now when we have this forward motion we have what's called drag, which is basically the main mass of the character, is right up here. That will not want to move. Go back to the laws of motion. Abody at rest will want to stay at rest. So that part of him will want to hang back. It doesn't want to move forward. So as this moves forward, from an animation perspective it will appear as though a force is pushing him in the chest.
When in reality it really is just the body itself wants to stay where it's at. So we can animate this by doing some keyframing. The first thing I want to do is go ahead and just drop those arms to his side. Just want to give him a little bit more of a relaxed pose. We will play with the arms and the rest of the body a little bit later, but I just want to start with the center of mass of the character which is centered around the hips. Now when we pose characters we typically pose starting with the hips and when we are working with these sorts of force problems we also a lot of times will start with the hips.
So I am going to go ahead and set a keyframe here at frame 1. Now I am going to move forward a little bit, maybe a couple frames, maybe three or four frames. Let's go to frame 5 and let's give the impression that that body wants to stay in place, so I am going to go ahead and rotate it back a little bit and move it back. So right there I want to basically drag him back. And you can see even right now it feels like he's got a little bit of force acting upon him.
It's starting to understand the flexibility of this character. But he is not going to stay back the whole time because this is moving at a pretty constant rate, so again he will tend to straighten up. So I am going to go back to frame 1 and copy that keyframe and then we're going to go to forward say about 10 frames or so, to frame 15, and I am just going to paste that keyframe. So now he goes backwards and now he kind of straightens up.
And then at frame 25, where he starts to move back, I want to straighten him up again. And then we can do with the opposite. We can go another couple of frames in, say about five frames again, and this time his body wants to keep going in that direction. So I am going to move him forward and then also rotate that a bit and make sure that his heels are not off the ground there. And again at frame 40, I want to go ahead and copy this and just straighten him up again and then go back to the very beginning and let's make sure that we've got a keyframe there.
So now what we've got is he's going backwards and forwards. So you can see that even right now we've got a much better sense of motion for the character. We've got a sense of force acting upon his body. Now one thing I'm noticing here is that we have a little bit of a bounce in the animation. Sometimes you have to be real careful in looking at these and you can kind of catch it, but notice how that as he comes past here he actually overshoots this a little bit. So right here he feels like he is a little bit far-forward and then he comes back a little bit.
It looks almost like he is kind of more of a spring. He has kind of got this kind of back and forth motion. Now this may actually be a problem that we can diagnose in the Graph Editor. So I am going to go into Window > Animation Editors > Graph Editor,and let's take a look at this. So I am going to go ahead and select his hips and let's take a look at the rotation curves for the hips. Specifically I'm rotating him along the X axis, so I am rotating him back and forth. So if I select the Rotate X curve immediately, let me go ahead and frame this by hitting F. Now what we have is he starts at 0, he goes down a little bit, he comes back up and the next keyframe is at 0, as is this frame and this frame.
But what I've got is I've got this curve it is kind of overshooting right here and then it undershoots, and that's what's giving me that kind of wobble in his motion. In fact, let me go ahead and highlight this and you can see how the wobble and the curve kind of match up. Now that we can see what the problem is it's very easy to fix it. One way would be to just to select these curves and unwind them, but the easier way is to select all the keys that are 0 and then all we have to do is hit what are called Plateau tangents.
What that does is that make sure that all of those are 0. So particularly here where it goes from a 0 to a 0, you want to make sure that these two sections are flat. Now once we've done that, you can play it back and now we have a very smooth motion. So this really is just the motion of the platform affecting the character. This is one of several forces that we are going to deal with. So let's go ahead and refine this a little more in the next lesson.
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