Is there a simple way in Python to move all keyframes in time in one go?

Coding Python Support
#1

I’ve a complex scene with a load of traditional keyframed animations going on - much of it from a baked physics sim.

So I can do a nice smooth overcrank effect (ie smoothly slow time down, so we can see part of the action in super-slow-motion), I need to render out frames at sub-frame intervals.

Blender can certainly render out non-integer frames, as it does if you use the Time Remapping feature, but I need more fine-grained control. I need to be able to render the scene at, say, 3.2 frames in, 3.75 frames, 3.96 frames etc.

The only solution I can see, given that I can’t directly tell Blender to render the scene at 3.96 frames in, is to use Python to move all my keyframes back by 3.96 frames, then I can just render frame “0”. Repeat for each frame I need.

I can do it manually by going to the Dope Sheet, selecting all keyframes, switching off Frame Snapping, and dragging the whole lot in one go, but I need to do it with Python - I need about 200 frames rendering.

Question: What’s the simplest way to move every keyframe in a whole scene back/forward in time by a certain amount?

  • Do I have to iterate through every object, every animation, every track, every key?
  • Or would it be better to approach it more like a macro: have my script do the motions I’d perform in the Dope Sheet to do the same thing?

Any suggestions for the easiest approach?

#2

If you want to change keyframes of all actions, you can do:


import bpy

for action in bpy.data.actions:
    for fcurve in action.fcurves:
        for point in fcurve.keyframe_points:
            point.co.x -= 3.96
1 Like
#3

Wow, thanks CoDEmanX - that looks so much simpler than what I was expecting to have to do. I reckon it’ll do the trick!

#4

Code needed adapting slightly - it didn’t move the keyframes’ bezier handles. Just for completeness, here’s the code I used:


    # theTime is the new frame time I need rendering (as a float) - obtained from a 
    # list of times cut and pasted from an After Effects Time Remapping track.
    # This chunk of code is executed for each frame:

    theOffset = theTime - prev_time
    prev_time = theTime
    
    # move everything to new position
    for action in bpy.data.actions:
        for fcurve in action.fcurves:
            for point in fcurve.keyframe_points:
                point.co.x -= theOffset
                # don't forget the keyframe's handles:
                point.handle_left.x -= theOffset
                point.handle_right.x -= theOffset
    
    # adjust the motion blur duration to half the interval between this and the last frame
    bpy.data.scenes["Scene"].render.motion_blur_shutter = (theOffset / 2)

    # insert your own render code here!

Thanks again, CoDEmanX - hugely helpful :slight_smile:

1 Like
#5

I have question post in here, I just want move last keyframe, can anyone help me, thanks!: