How to animate the speed of video?


(thrilledburst) #1

I was thinking, instead of rendering a whole bunch of frames and then animating the speed of the output video, how can I save myself time and animate the speed on the first render?


(yogyog) #2

Are you talking about using the “Speed control” effect in VSE? If so - yes! you can do this to a scene as well.


(thrilledburst) #3

Yes, that’s exactly what I’m talking about. I just don’t what exactly is that called for the scene itself. Is it time remappping?


(thrilledburst) #4

Nope, looks like time remapping cannot be animated.


(yogyog) #5

Whoops - I meant Speed Control Effect in VSE.


(thrilledburst) #6

Yeah, but isn’t that only for videos? How do I do the same to the whole 3D scene?


(3pointEdit) #7

If you make an animated 3D scene that only last 20 frames, you can then import it as a scene strip in another scene’s VSE. Here you can apply a VSE Speed effect to it. You can ramp or keyframe the speed of this effect, and Blender will render all the new frames to compensate for the slow motion or drop frames when you speed it up.


(thrilledburst) #8

Hmmm what you’re saying does make sense to me to a certain degree, but I have very little experience in that area of Blender, so I’ll have to look it all up. Thanks!


(thrilledburst) #9

I figured it out and it works perfectly, thanks a lot! I was just wondering, is there a way to preview what the output will actually look like instead of just rendering everything in low quality every time?


(ar2) #10

In a quick test it worked out of the box for me:
speed-test.blend (87.8 KB)


(thrilledburst) #11

Yes, it works for me too, but the problem now is how can we preview the rendered version? Because I wanna animate speed of true displacement which you can’t see in solid shading.


(ar2) #12

Sorry in this case I dont know a solution, I thought, that you needed only the movement.


(3pointEdit) #13

Perhaps you could render with border selected? You’ll still have to render the frames but not the whole frame, unfortunately this doesn’t help in the VSE as I don’t think it allows rendering with border active.


(thrilledburst) #14

Yep, can’t render with border active. Eh, I guess I’ll just have to do more planning before speed controlling the scene.


(3pointEdit) #15

Could you replicate the border crop by rendering a mask in front of camera using some geometry with an empty material slot (does not allow bounces)? You’ll get the whole scene dimensions and its compatible with the VSE, the black areas should render much faster.