Smooth acceleration in a motion path

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Level 1

54 points

Smooth acceleration in a motion path

I have what I consider to be a very simple requirement. I wish to create a move on an imported still image. I want to select a zoomed-in segment of the image, position A, hold on this for a time, then pan to the right across the still image to a new position, position B, and hold again. Using keyframes I can create this motion path, which has a constant speed during the move, ie a jump start and a sudden stop. I want to build in smooth acceleration and deceleration. I have consulted the manual (V III pg 278), but following that method does not provide the answer. What it does is modify the path so that, for instance, if position A is framed to exclude some of the original image at its left edge, when the move starts it pans LEFT a short way onto the unwanted area before panning right as planned. A similar problem happens at the other end of the move. I don't think this is finger trouble when adding the Bezier handles, it happens every time.

I have scoured the manual and the help files but can find no other solution. Does anyone know how to do it?

Many thanks
John

G4 Quicksilver 867, G4 Powerbook 15", Mac OS X (10.4.10)

Posted on Nov 25, 2007 4:47 AM

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Answer 1

Nov 25, 2007 7:29 AM in response to John Howarth

hat it does is modify the path so that, for instance, if position A is framed to exclude
some of the original image at its left edge, when the move starts it pans LEFT
a short way onto the unwanted area before panning right as planned.
A similar problem happens at the other end of the move. I don't think this
is finger trouble when adding the Bezier handles, it happens every time.

Not sure what you're seeing on your screen that is leading you astray but if you have followed the manual, you have turned the keyframe into a smooth point. For whatever insane reason, FCP's designers decided this action places TWO control points on the motion path, one for speed, one for the curve. You must carefully grab the point for speed and you probably have to reposition the one for the shape of the path since it has apparently created a bit of a curve in your path.

Easier to show you than to explain it, can't do that, tho.

bogiesan

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Answer 2

Nov 25, 2007 7:34 AM in response to John Howarth

John, that feature has confounded almost everyone who has tried. I spent a day with it and finally decided that Motion did a better job and was a lot easier. If you can find and play with the almost invisible bezier handles (in the Canvas) on the start and end keyframes, you might get close to what you want. The secret seems to be in adjusting the lengths of those handles until the curve is smooth and you don't get the "wrong way" effect. You can grab the end of the handle and make it longer or shorter and swing it on an arc. Try making the handles shorter and see what happens.

However, even when I've gotten rid of the "wrong way" bump, the start and stop are never really smooth enough.

Motion is able to make a very gradual ease-in or ease-out. With Motion, you might have to go into the Keyframe Editor and change some of the keyframes to Bezier interpolation. I believe the x/y position defaults to bezier, but the scale does not. This is a small hassle, but not nearly as bad as the FC keyframes.

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Answer 3

John Howarth Author

Level 1

54 points

Nov 25, 2007 7:58 AM in response to tbrookskazoo

It's kind of re-assuring to know it's not just me. Maybe I have to learn Motion, although when I glanced through the manual I couldn't find an easy way in to do this. Can anyone recommend any rostrum software? DigiRostrum by Lumidium has come up, made with the endorsement of Ken Morse, (the rostrum cameraman who holds the Guiness Book of Records for the most tv screen credits, for those who need to know), so it ought to be good, but annoyingly it's Windows-only.

John

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Answer 4

Nov 25, 2007 8:06 AM in response to John Howarth

The secret seems to be in adjusting the lengths of those handles until the curve is smooth and you don't get the "wrong way" effect. You can grab the end of the handle and make it longer or shorter and swing it on an arc. Try making the handles shorter and see what happens.< </div>

Not really, the secret is in finding both of the control points on the path and figuring out which one does what to which parameter.

an anyone recommend any rostrum software? < </div>

There are several. Phototomotion (or is fotoinmotion?) seems to be popular. You can search here for the "ken burns" rubrick.

bogiesan

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Answer 5

Nov 25, 2007 9:27 AM in response to David Bogie Chq-1

Not really, the secret is in finding both of the control points on the path and figuring out which one does what to which parameter.

True David. The inner control point adjusts the acceleration, or that's what it looks like to me. On the other hand, I can't really get moves that are both smooth and predictable with FCP. I'm sure it's possible to get a feel for it with practice, though.

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Answer 6

Nov 25, 2007 9:56 AM in response to John Howarth

"Can anyone recommend any rostrum software?" AfterEffects does this kind of ease beautifully and once you explore the options available by control clicking on the keyframes you'll be home free.

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Answer 7

Nov 26, 2007 8:53 AM in response to tbrookskazoo

?> True David. The inner control point adjusts the acceleration, or that's what it looks like to me.

There's a huge section of the manual dedicated to editing motion paths.

On the other hand, I can't really get moves that are both smooth and predictable with FCP.
I'm sure it's possible to get a feel for it with practice, though.

Possible, frustrating as heck. It was a hugely stupid design decision, never should have been this way. Post your dissatisfaction in the FCP Feedback folder and tell them Bogie sent you.

Use Motion? Tons of fun if you don't have an After Effects Prejudice that prevents you from comprehending Behaviors (like I do, I hate Motion).

bogiesan

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