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In programs like After Effects you can select a speed graph to edit the speed/velocity of your animation. i.e pixels/sec:

enter image description here

In blender I’m attempting to do this in the graph editor, but I’m accidentally changing the actual start/end values of the object’s location/rotation rather than editing the speed/velocity/influence of the object’s key frames. I’m only looking to edit the speed between the keyframes.

I’ve read about “evaluation time” of paths in blender. Is there something similar to this for solely the speed/velocity of the object? I guess it would be easiest to call it “custom easing”

Thanks!

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The overall speed between keyframes can be only changed in the dopesheet or graph editor moving them, there is no built-in function to use a curve to control the timing.

To get this behaviour, you can use the action constraint: a single channel of a "controller" (like X loc of an empty or a bone) can be used to trigger the action of one or more objects or bones (like moving X loc 10 units means perform the action from frame 20 to 80).

Once the constraint is created, it can be easily copied to others objects or bones involved in the action to be retimed (i.e. select all objects involved, shift select the constrained one - last selected is active - and use the "copy selected contraint" function.

If the action is based on bones, the constraint has to be copied to all involved bones.

enter image description here

Another method is to load a rendered image sequence and retime it using a curve to control.

To do this, add an image sequence as plane, create a custom property, edit its name and its limits (in my example "timing", and 1 - 80, the number of images on the sequence).

Then hover over its value and right click "copy as new driver".

Paste the driver on the "offset" value of the image sequence node in the shader editor.

Then edit the driver changing its result form "Average value" to "Scripted expression", tyiping in "var - frame# + 1" (in my example, as the name of the custom property is set to "timing", the expression becomes "timing - frame# +1).

Now you can animate the custom property value and edit its curves in the graph editor.

enter image description here

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Animate NLA strip time.

SImilar to evaluation time in a path

enter image description here Red without and blue with animated strip time. Green scaled from 1:250 to 1:100

For example sake I have an animation

enter image description here

that moves a cube from -10 to 10 in 250 frames, (by simply setting x locations inserting kf at frame 1 and 250)

That's the animation. Now will drop this action down to the NLA editor.

enter image description here

Check and expand animated strip time. Keyframe the time to use in the action.

As an example, instead of slowly crawling from -10 to 10 across 250 frames, will get to 250 frames in 100, then go "backwards in time" in the next 150.

enter image description here

Scale the strip.

(Note for wholesale linear speed changes can instead alter the strip's start and end frames.)

enter image description here eg scaling the action to 100 frames

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