Replacing the writing on a rotating licence plate – am I on the right lines?

[Bruce Breidbart]

Hi Simon,
I’ve posted my version of the license plate in the above response. It’s a little jerky as it follows the movement. The only thing I was hoping for to put this project attempt to bed, was a smoother track
so to speak of the exiting/entering license plates. One thought I had was to analyze the movement, that didn’t work so well. So I key framed every X rotation & X and Y position. It was impossible for me to see exactly how much to rotate each keyframe, hence my problem. Gareth posted his timeline, but sadly it didn’t help me in that respect.
I guess purchasing Mocha Pro might solve this problem quickly, but I’m not sure that’s what Gareth did.
Your thoughts would be gratefully appreciated.

thanks in advance

BB

[Simon Ubsdell]

[Bruce Breidbart] “One thought I had was to analyze the movement, that didn’t work so well.”

It’s not something you can successfully track with Motion, I don’t think, although Mocha might be able to handle it.

[Bruce Breidbart] ” So I key framed every X rotation & X and Y position. It was impossible for me to see exactly how much to rotate each keyframe, hence my problem. “

While that would seem like the perfect solution, it will always result in a jerky movement. You need automatic interpolation rather than any manual adjustment – even if you got every frame “spot on”, the resulting movement wouldn’t appear smooth on the run.

Your best bet is to set a keyframe for the start and end and – by trial and error, I’m afraid – work out the interpolation method used in the original animation.

If you set both keyframes to bezier you could probably go into the keyframe editor and tweak them to match as you view the composite.

It might even be that a straight linear interpolation is what works best and was what they did originally in the movie. Not having got the live action plate in front of me, I can’t tell you for sure, sorry.

EDIT – you talk about keyframing the Y position – but you really shouldn’t need to be doing this.

Simon Ubsdell
hawaiki.co

[Gareth Randall]

[Bruce Breidbart] “I guess purchasing Mocha Pro might solve this problem quickly, but I’m not sure that’s what Gareth did.”

I didn’t use any motion tracking at all. Just keyframed the X rotation.

I’m no Motion guru, but if you want to post up your project file (as long as it’s Motion 4, I don’t have 5) I’m happy to have a look at it and see if I can get it to match mine.

[Bruce Breidbart]

Gareth, I’m using Motion 5. But I was able to see your timeline when you posted it, interesting.

I guess my question is, X rotation will only rotate the license plate,
how do you follow the movement off the screen if it doesn’t need the
X and Y positions adjusted. Obviously I’m missing something.

BB

[Gareth Randall]

As long as you’ve got the camera adjusted correctly and the anchor point of the plate moved back in Z space, then adjusting the X rotation will make the replacement plate follow the rotation of the original.

I’ve just tried deleting the keyframes of the missiles plate in the project I uploaded and re-animating it. This is what I did:

Go to the Anchor Point parameter of the new plate, and set Z to -151.65. X and Y stay at 0.

Line up the new plate over the original, then go to frame 4 (where the movement begins), and set an X rotation keyframe. Make the value -7.0

Switch off the new plate, or lower its opacity, so that you can see the movement of the original. Move forward to frame 18. This is where the original plate is edge-on to the camera. I trimmed the new plate graphic to end there.

I moved one frame back to frame 17 and set another X rotation keyframe for the new plate. Then I adjusted the X rotation until the position of the new plate matched the original – the actual value was -77.0.

Then I just turned the opacity of the new plate back to 100% and played. And… that’s it 🙂 The movement matched pretty much exactly. Literally just two X-rotation keyframes going from -7 to -77, nothing more.

[Bruce Breidbart]

Thanks.
As it turned out you gave me the key to success at least 3 posts a go.
” For the actual rotation, I moved the anchor point of the plate back in Z space just a little”.

Adding a camera & 3D is a little new to me. I moved past the most important part of pulling
this off because I didn’t fully understand it, not sure I do now, but it’s what makes it work and
I’ve got it working, boy do I have lots to learn.

Thanks for taking the time.

Now if I can only figure out how to take my name off the Top row of the Motion blog.
When I tried to send my video along with my post I must of hit the wrong key.

BB

[Gareth Randall]

[Bruce Breidbart] “As it turned out you gave me the key to success at least 3 posts a go.
” For the actual rotation, I moved the anchor point of the plate back in Z space just a little”.”

Aha 🙂

Yes, you have to think in terms of how the plate-rotating mechanism would work if it was real. That gives you the clue as to where you need to position the anchor point around which the plate will rotate. If it was real, then obviously the plates would be attached to a rotating bar further back inside the car’s bumper, so then it’s just a matter of experimenting with pushing the anchor point back in Z space until you find the distance that works to mimic the rotation of the original plates.