From the course: 3ds Max 2021 Essential Training

Editing keyframes in the Track Bar Timeline - 3ds Max Tutorial

From the course: 3ds Max 2021 Essential Training

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Editing keyframes in the Track Bar Timeline

- [Instructor] The track bar timeline, not only displays key frames for the selected object, but also allows us to edit those key frames in the time dimension. Let's take a look at editing keys in the track bar. It's called the track bar precisely because it gives us access to visualizing and editing animation tracks, or channels of animation data such as position and rotation key frames. With the select object tool active, click on the animated object, which is the camera. Key frames for the selected object are displayed in the track bar and we can simply click on these to select them. A selected key frame is highlighted in white. Then we can just click and drag on it to move it in time. I can move it to an earlier point in time such as frame 30, and then press play. What we see is the first half of the animation goes very quickly and the second half goes much more slowly. We can move a key frame to a different point time, but we're not changing the key frame value. In other words, we're not changing the position of the camera, we're merely changing when it is at that position. All right, so if I move this to a later point in time, such as frame 100, then the first half of the animation will be very slow and then it will speed up towards the end. Okay, I'll stop and rewind that and bring that back where it was at frame 70. We can edit multiple key frames at the same time. Just drag a selection rectangle around multiple key frames and they're all selected and then just click on any one of them to move them all as a unit, but realize that we can move the key frame beyond the current time range. Right now the last key frame, or the third one, is no longer visible because I moved it outside the current active time segment. Okay, I'll move this back where it was, and now I can see all three of those key frames again. Even better than this, we can move and scale selected keys as a unit with a cool feature called selection ranges. Rewind back to frame zero and enable this feature. Right click on the track bar and get a contact sensitive pop up menu, choose configure, show selection range. This reveals a black bar down at the bottom because we have two or more key frames still selected. If I click to deselect all those keys, that bar disappears. If I select just two of those keys, then the selection range changes size accordingly. To move selected keys in time, just click on the selection range, and drag from left to right. Be careful once again, because it's very easy to move key frames out of the current time range and as we can see when I do that in this case, my selection range bar actually disappears. Okay, I'll bring that back where it was. To scale the speed of animation within the selected range of key frames, you can drag on the handles at either end. I'll select all three of those key frames and click on the handle on the right side and drag to the left and I'm squeezing time for these key frames. I'm moving their positions in time while maintaining their relationship in time to one another. So I'll speed that animation up, I'll bring that last key frame to let's say frame 80, and then press play and we can see that the animation is much faster. All right, I'll stop that and rewind once again. By default, any editing of key frames in the track bar will cause the keys to snap to whole frame numbers, so it's going to round off any proportional scaling to whole frames. This will change the time relationship among keys. If you repeatedly scale key frame regions, you'll introduce a series of round off errors and shift your key frames around in undesired or unexpected ways. If I scale this all the way down, let's say I grab that selection handle on the right and scale this down to very small, and then scale it back up again, I'll select those keys and scale this back up to where it was at frame 149, now this center key is no longer on frame 70 where it was. Now it's on frame 75. So that's just a gotcha, be aware of that. If you need to maintain precise timing, you can disable snap to frames. Right click on the track bar and choose configure, and disable snap to frames. And then, you can do successive scaling operations without introducing very much error and scale that all the way down and then scale it all the way back and that center key frame seems to land on frame 70. But what's happened here is actually these key frames have landed on fractional frames. The key frame is actually between frames. Remember that the internal time base of Max is 4800 ticks per second. Unless we set the time configuration to display ticks, there's no indication anywhere in Max that we're dealing with fractional frames. Other than the fact that these key frames are now very narrow, they're displayed only a few pixels wide. Currently, that's my only clue that these are key frames on fractional frames. And why does it matter? Because key frames on fractional frame numbers could cause big problems. For example, in a bouncing ball animation, the key at which the ball is supposed to touch the ground could easily end up between frames. And then, if we rendered the shot, there would be no rendered frame on which the ball visibly touched the ground. The key itself would never get rendered. We'd only see the adjacent whole number frames. If you disable snap to frames, remember to re-enable it when you're finished animating and then snap everything to whole frames. The process for that is to re-enable, snap to frames, and then select all the keys and then just move them, release the mouse and move them back, and that seems a little clunky, but it works. There actually is no command to just round off all selected keys to the nearest whole number frame. We have to move them and then move them back. The other solution to this round off error problem limits our creative freedom, but it is much less error prone and that is to leave snap to frames enabled and just try to never perform more than one successive scale operation with the selection ranges. If you need to scale something, do it once and try to do it only once. Snap to frames is a destructive option and it needs to be treated as such. That's how to edit key frames and key frame ranges in the track bar.

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