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Time remapping slope

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Jared GardnerTime remapping slope
by on Aug 28, 2013 at 4:42:18 pm

I'm looking at the graph but I'm a little confused. I've time remapped some stuff to have a frame extension in a place or two, but it seems to have switched the normal playback rate from 1.00 second/sec to 1.01 second/sec. The frozen frames are also playing back at 0.01 seconds/sec and not 0.00 seconds/sec.

I also have a couple mistakes where it's slower than it should be but when I try to edit those two points, at the top to get it back to 1sec/sec, the first little square moves fine but the 2nd one where it starts to slow down again only changes the velocity.

Did I make a booboo somewhere? I can go back and change them individually if so, but this might be how After Effects does this by default.


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Darby EdelenRe: Time remapping slope
by on Aug 28, 2013 at 5:25:54 pm

It sounds like the values of your keyframes could be incorrect. Alternatively they may appear to be correct but actually be incorrect due to a difference between the frame rate of the composition and the frame rate of the footage.

For example, if you had a 120 frame clip that runs at 30fps and you wanted exactly 1.0 seconds/second you'd need to verify that the time remap keyframe on frame 0 of a 30fps timeline has a value of 0 and the time remap keyframe on frame 120 (the last keyframe) has a value of 120 (all keyframe values are in frames in this example). This works because the frame rate of the footage and the frame rate of the timeline are the same.

If, however, that 120 frame clip runs at 25fps and you have it in a 30fps composition then the last time remap keyframe with a value of 120 should be on frame 144 of the timeline. If you were viewing time in timecode instead of frames this means that at frame 4:24 of your 30fps timeline your keyframe should have a value of 4:20 which may appear to be wrong but is in fact correct.

Intuition might lead you to adjust the the timeremapping keyframes to match the corresponding time/frame values in the timeline (changing the keyframe to 4:24 at 4:24 for example), but this will result in an incorrect speed if the frame rate of the footage and the comp are not exactly the same. I chose 25fps and 30fps as my examples because the difference is more extreme, but if you had 29.97fps footage in a 30fps comp or vice versa you could run into the same problem; the error would just be very small.

For the other problem you mention, there are three ways to adjust the speed of an animation:

1) Adjust the incoming/outgoing velocities of the keyframes.

2) Move the keyframes in time.

3) Change the keyframe values.

It sounds like you're doing (1) when you should probably be doing (2). If you have a 1 second/second speed between two keyframes and you increase the velocity of the first keyframe without moving the keyframes then the speed must dip below 1 second/second before the second keyframe in order to keep the area below the speed graph constant. The area below the speed graph (the integral of the speed) between two keyframes corresponds to the total change in value from the first keyframe to the second keyframe. Since the total change in value hasn't been altered (you haven't (3) changed the keyframe values) and the time over which it's changing hasn't been altered (you haven't (2) moved the kefyrames in time) the graph must run slower later in the animation to make up for running faster earlier.

Darby Edelen


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Jared GardnerRe: Time remapping slope
by on Aug 28, 2013 at 5:55:09 pm

More than enough info, thanks. The problem was that when I was dragging the keyframes, I forgot to select the last keyframe as well. All is going at 1.0 second/sec now that I was more careful with dragging that last keyframe out along with the first one to extend that frame.

Something that I'm still wondering though is that for the extended frame, it slows to 0.01 second/sec. Is that the default?


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Darby EdelenRe: Time remapping slope
by on Aug 28, 2013 at 6:03:46 pm

[Jared Gardner] "Something that I'm still wondering though is that for the extended frame, it slows to 0.01 second/sec. Is that the default?"

No, 0 seconds/sec is correct for a frozen frame.

Darby Edelen


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Jared GardnerRe: Time remapping slope
by on Aug 28, 2013 at 6:26:27 pm

I'm apparently not doing this right if it's supposed to be 0.00 seconds/sec. Here's my current method:

1) Add time remapping
2) Go to a frame I want to pause and create new keyframe
3) Move over one single keyframe ahead and create another keyframe
4) Drag the keyframe from (3) and the very last keyframe at the end in unison to extend it

I looked at two tutorials for it and I'm following it to a T. Are you sure it's supposed to be 0.00 seconds/sec? It goes to 0.01 seconds/sec no matter what.


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Darby EdelenRe: Time remapping slope
by on Aug 28, 2013 at 7:35:15 pm

[Jared Gardner] "1) Add time remapping
2) Go to a frame I want to pause and create new keyframe
3) Move over one single keyframe ahead and create another keyframe
4) Drag the keyframe from (3) and the very last keyframe at the end in unison to extend it"


You do not want to move one frame ahead and create a keyframe as in your step (3). You should:

1) Add time remapping
2) Go to a frame you want to pause and create new keyframe
3) Copy the keyframe created in step (2)
4) Drag the keyframe from (2) and the very last keyframe at the end in unison without moving the current time indicator.
5) Paste the keyframe from step (3) at the current time indicator so that it is on the same frame that the original keyframe from step (2) was.

The values of the first and last keyframe of a paused section should be exactly the same, not 1 frame different.

Darby Edelen


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Darby EdelenRe: Time remapping slope
by on Aug 28, 2013 at 8:50:21 pm

Alternatively you could make the keyframe from your step (2) into a hold keyframe after you've extended the frame.

Darby Edelen


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