Skill Level Intermediate
- [Instructor] 3ds Max provides some very cool tools in the curve editor to modulate the animation function curves. Specifically, we have the multiplier curve and the ease curve. The multiplier curve allows you to change the value of the key frame or channel or track, and the ease curve allows you to change the timing or the speed. And we'll use them both in this demonstration. I've got a little bouncing ball here, and we can see its motion path.
If you've never used 3ds Max motion paths, you can check that out in another course, which is 3ds Max 2018 New Features. So let's play this through and see what we've got. It doesn't really look like much. I've designed this to best illustrate the power of the multiply and ease curves. We've got the ball bouncing in place here at the end, and we can cause that bounce to decay or lose energy with the multiplier curve.
And we can also cause the ball to bounce more times in the same distance by slowing down the curve or using an ease curve. So let's check this out. Let's select the ball, and with that ball selected, we can now see the key frames on the motion path, and notice that the ball's traveling in a straight line here. Now, we could accomplish something similar with the motion path, but it would still be a little bit tricky to change the speed of the ball while maintaining this linear path through space.
But with the ease curve, it's going to be very easy. All right, so that ball selected, let's go into the curve editor. And with the middle mouse button, we can position the curve editor. That ball selected, we've got the position and rotation tracks visible. We want to apply a multiplier curve to the Z position, so select Z position, and we can frame the curve here using this button down here, frame horizontal and value extents.
And you can see that we've got some key frames here, and the ball is bouncing the same height each time. With that Z position selected, let's add the multiplier curve, and go in the curve editor menus here to curves. Apply multiplier curve. Once we've done that, we can see there's a little plus sign next to Z position. Open that, and there's a multiplier curve subordinate to the Z position curve. If we select multiplier curve, we see this turquoise line down here, and it's got a constant value of one, meaning that it's multiplying the position by a value of one throughout the time.
Now, we can frame this up a little bit better. We can use the zoom region tool here, drag a rectangle around that, and try to get it so that we have the value from zero to one taking you the entire vertical space here. It's actually a little bit tricky to do it with these tools down here. So what I recommend is you use the keyboard shortcut or hotkey, which is Control + Alt and middle mouse, and with that three-finger salute, you can drag left and right or up and down to scale the curve the way you want it.
And use the middle mouse button to position. And I just want to make sure that I'm taking up the full linear distance left to right here. So down here, we've got the buttons frame horizontal and value extents. Click on frame horizontal extents. Now, in some programs, we have the ability to normalize the display of the function curves. In other words, we can view multiple curves and have them all be visible on the screen at the same time, even if they are of radically different values.
So our Z position is in the range of hundreds, but our multiplier curve is in the range of one. And like I said, with some programs, we can actually see them both on the screen at the same time, but unfortunately, in 3ds Max, there's no mechanism to normalize the display. But there's a workaround, which is to display two curves in two separate curve editors at the same time. Down here in the timeline, we have a button, open mini curve editor. Click on that, and now we've got another curve editor.
We can expand that, make it taller, and we want to pan around and find our ball, and here's the Z position. So select Z position there, and we once again want to frame it. So we've got another horizontal and value extents button here. So this is for the mini curve editor. So you can click on that. And our Z position curve is not being displayed because it's out of range here, so let's go ahead and click on frame horizontal value extents.
And now we're getting what we want. There we go. So that's the unchanged, unmultiplied Z position curve, and just so we have a one-to-one correspondence between these two panels, we want to click on frame horizontal in both of them. Okay, so now here's where the magic begins. Back here in this top curve editor, for the multiplier curve, let's grab the move keys tool, and we can move these up and down. So we can select one of these guys here and hold down the Shift key, and that'll constraint the movement, either horizontally or vertical.
So hold down shift and drag. And as I bring that down, you can see that instantly this curve is fading out. Very cool. So I know exactly what I want here, in fact, so I'm going to just plug it in. I want the multiplier curve to begin at around here, so I'm going to select the first key frame. And I'm going to set the key frame frame value to frame nine. And hit a nine down there. And the value is going to stay at one.
And down here, for this last key frame at frame 100, we want it to have a value of zero. Type in a zero. Now, for this demo, I have simplified the workflow, and I'm just scaling that curve down the zero here. And that's in world space. And what I've done here is I've actually moved the ground plane down a little bit to account for that. In an actual production, I might link the ball to a dummy object in order to fine-tune the distance between the ball and the ground. But again, here, I've vastly simplified the workflow, just for demonstration purposes.
All right, so the curve that we want to see here is basically what we have. We want to see a slow out of that first key frame at frame nine, and the slow in here at the key frame at frame 100. And so let's see what that looks like. I'll close the curve editor, and we can rewind and play this back. And so we can see that the multiply curve is working. The bounces are becoming smaller over time.
Cool, so that's how multiplier curves work, and now let's look at an ease curve. And the ease curve, once again, will allow us to change the timing, and you could do that in other ways. Like I said, we could use the motion paths, but it might be tricky to keep this trajectory of motion path perfectly linear here as seen above. Likewise, if we try to edit the X and Y position curves manually in the curve editor, it would be very difficult to maintain this linear path. So I'll go back into the curve editor, and here, we've got X and Y position.
I want to select both of those, and we can frame their horizontal and value extents. And with both of those selected, we'll add an ease curve. Back up in the curve editor menu under curves, choose apply ease curve. And the same ease curve is applied to both the X and Y position. It's instanced. If I go to X position and open that up, we'll see ease curve, and that's in bold, indicating that it's instanced somewhere else.
When I edit this ease curve, I'll be adjusting the timing for both the X and Y position. Down in the mini curve editor here, let's display the X and Y positions. So I can select both of those with the Control key and click frame horizontal and value extents, and we'll change up the timing. So here's our ease curve. We've got three key frames by default. There's one at frame zero, one at frame 50, and one at frame 100.
And again, this is a very simplified workflow in which I've set it up so that my timeline is exactly 100 frames, and that gives us a one-to-one ratio with the ease curve, which is a percentage value. So in other words, here at frame 100, we have 100% of our timing. And at frame zero, we have zero percent. And at frame 50, it's 50%. But in the real world, it wouldn't be quite that simple. Your timeline would not be exactly 100 frames.
But again, I've simplified it for demonstration. So let's change this up. I'll select that second key frame, and I could use the move keys tool to just position that, but I already know what I want, which is, once again, I want the key to be a specific time at a specific value. So we have our inputs here. I can set that key frame to occur at frame 14, so I'll type that in. And I want it to have a value of 14 as well.
And as I do this, you can see the timing change here. All right, cool. So we don't want to use the entire range of time. As you can see here, we only have 30 frames of animation. But we can stretch that 30 frames of animation out to 100 frames by setting this key frame here to occur at frame 30. So I'll select that last key frame, and down here, we can set its value to 30.
Type in 30, press Enter. And now what we're doing is we're basically stretching out that time, and we can now play around with the overall shape of this. So we want to, once again, frame the horizontal and value extents. If we need to, we can use Control + Alt and middle mouse. and with the shape of the curve here now, we're actually moving backwards in time, 'cause we're going up and then back down again.
So let's fix that. Select that key frame there, and set it to auto tangents. And this one here, we'll also set to auto tangents, at least to start with, and then click the tangent here and adjust the shape. Because what I want to achieve here is a linear time transition here. So we want that to be basically linear, which means we're not adjusting the timing in the first 14 frames, and then we're going to slow it down.
And we can play around with that a little bit, stretch that, but we just don't want this curve to ever exceed the value of 30. So if we do that, the ball will actually slow down and go backwards, so we don't want that. All right, cool. So you can see here now that we have animations stretching out all the way to frame 100, and we can close the curve editor. We can close the mini curve editor and size that back down again, maximize the camera view, select it, and use Alt + W to maximize it.
And rewind and play it back. And as you can see, we haven't dealt with rotations, but that's all we can do in a single movie. But we've applied the ease and multiply curves. Let's take a look at a rendered version of that. Here's the rendered version of this in which, again, we don't have any rotations, but we can clearly see the power of the multiplier and ease curves in order to modulate the shape of the function curves for animation.
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