Curve with path cannot be keyframed -- help needed

I cannot figure out why I get this error

I’m trying to set keyframes in Evaluation Time box to alter the airplane speed during travel in file “boing_stearman_northbynorthwest_06.blend” – unsuccessfully. I receive this message which give me no sence_


Though In the file “boing_stearman_northbynorthwest_06a.blend” this results in no errors.


The files: (1.2 MB)

What is the catch. Can any telll what is my problem is?

Kind regards

Hi Mikael,

You can’t keyframe that animation because you have an f-curve generator deciding on the animation:

Delete the generator, then you can simply key the evaluation time as you like, and you’ll have full control over the f-curve shapes:


Hello Damian
Thank you so much – with your visual help I got the grasp nailing the proper procedure: The correct steps are precisely as you stipulate. In my own words:

  1. First select the object – then the path
  2. Select ctrl-p (Follow Path, checkmark: “Object data tab/Path Animation”)
  3. Go to Graph editor
  4. Select curve “Evaluation Time”
  5. Delete modifier (“n”-panel, “Modifier” tab,“Generator”) – *)
  6. With curve “Evaluation Time” selected one can now control traveling speed

*) As a matter of fact you can select “Additive” and thus keep modifier open and curve editable. Yet I experience this make stuff acting a bit oddly … more testing needed :slight_smile:

Kind regards, with gratitude