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Body motions are full of accelerations, decelerations and changes in direction. When the target reaches an extreme in its motion and changes direction that's a very good place to plant a keyframe. For this video I am using the coffee cup clip from the Lesson_03_Media and the Extreme's Mocha file is in the Project Media folder. The first thing we do is study the clip and plan accordingly. We are going to be rotoscoping that coffee cup, so we want to find the extremes of the motion.
And there is actually several different extremes in this clip. So let's go find them, I'll stop the playback, jump to frame 1. I will scrub the timeline looking for the first extreme. There, right about here where the coffee cup changes its horizontal motion and starts to go up, so there is one. There is two, it reaches the top of the motion, there is three and then there is four at the end okay.
So let's do some rotoscoping on extremes. We'll start by turning on the little coffee cup shape that I made, select that. I am going to turn off the Tangents to make it easy to see. Let's zoom in and find that first extreme, so I were cruising through the timeline, and we get little closer, select all my control points. Okay, so I am single stepping through that clip looking for the change in direction.
And it's coming down, down, down, then it starts to do kind of a roll over to the side, I am going to call this, the start of this vertical climb, okay in this point, it's actually still going horizontally from the beginning of the clip. All right, so that'll be my extreme, so I'll pick up my shape and I'm not going to be placing this very precisely, because that'll just take way too much time fiddling control points. We're just trying to get the technique of keyframing in extremes, okay that's my first keyframe, so I'll zoom out, pan down and come up to find the other extreme here let's zoom in, we are going to try to get very precise, find out where that motion changes direction.
It's going up, up, up, up and now its going over to that, okay this is my last up frame right here. All right zoom out, grab our spline, bring it up here, zoom in position it, little rotation here, fine tune the position.
I don't want to spend too much time fiddling control points, because the cup has changed shape. It's tilted away from us, but we will make a few small adjustments here and call that good. We zoom out again, pan down and we look for our next extreme somewhere in here, zoom in, in single step looking for the action coming down, down, down, down well there it starts to turn, so it's got vertical motion here and then starts to roll into a rotation there, so we'll call this our last frame, our extreme.
Zoom out, pan down, grab our spline, zoom in, pan up, rotate and little bit of alignment. Okay, go home to the viewer. I'll select all of the control points, so we see the keyframes on the timeline and now I can jump back keyframe, keyframe, keyframe.
So we've got four keyframes at the extremes of motion. I am going to set the out point here, and I'll play the clip and even though spline lines up with the clip on our keyframes, you can see it's way off in all the frames in between. So let's go in and detail just one section finding all those accelerations and locking it together. We will stop this. Let's use this section here so I am going to go this keyframe, set the end point here go to that keyframe and set the out point there.
Now I expand the timeline, so we can focus on just this one section. Remember our strategy is always to divide and conquer, so we are going to work this little section. As we'll see real world objects accelerate and decelerate. The problem is the interpolation between keyframes is always linear, a nice straight linear motion. Now let's see what that means. I'll scrub through the shot and come here to the little and by they way that seems to actually kind of line up there in the middle, so I am going to lock this down and give it a keyframe, but because of the coffee cup's velocity is constantly changing, and the interpolation of the spline is simple linear motion in one frame it's widely off.
All right no worries. Let's use some Bifurcation to lock this thing down, not too bad. I don't have an exact little frame. Remember, we would like to have a exactly divisible by two or our keyframes, but that often doesn't happen in the real world, so let's position this guy here, we'll zoom in a little bit and then we'll go halfway here, position that.
These two keyframes are on very nicely but the in-between is off, so again, we've reposition that. I'll bounce between these two keyframes with the up and down arrows so you can see it's on very nicely on the keyframes, but we go to middle frame its off, all right so, touch that up. Then we come down to this section here, Again, if I bounce between the keyframes with the up and down arrows everything is fine on the keyframe, but if I come forward one frame, I am off again, because the accelerations and decelerations of the real world.
That frame is off to so, we get that guy on there. All right, so we're setup here. Now go work at the other half of the clip. Over here I'll try to pick a mid-frame, pan down and as we can see we're way off all right so, we position this guy here. Now I am going to bounce between these two keyframes with the up and down arrow keys and those guys are fine, but if I go to the in-between frame I am off okay acceleration again, okay we'll just do this okay.
All right, my last segment here, I will bounce between those keyframes up and down arrow they are fine, they are fine okay. I'll come to a middle frame way off all right, reposition that, come to that frame in-between these two here and of course again, way off and then we'll come over to the remaining little section, okay these two frames are off.
This keyframe is fine. That keyframe is fine, I bounce between the keyframes. Life is good. get on to the in-between frame life is not good so I'll have to adjust. Next frame again it's off so I'll tighten that up okay. Go home to the viewer, we'll play the clip okay we turn the Mattes on, play the clip see how it looks all right.
Now let's go look at the white Matte. I'll turn off the Mattes go to the clip pop up, so I'll select the Matte for coffee cup layer and now see my black and white matte. Let's turn on some Motion Blur and now we'll play our clip. Planting keyframe on the motion extremes will give your rotos more realism in their motion.
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