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# Acceleration problem with Position Keyframes

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 Acceleration problem with Position Keyframes on Nov 17, 2015 at 3:51:41 pm

This is doubtless a simpleton's question, but I've as yet been unable to crack it.

In simple flybys, when an object enters the frame large and moves away from the camera as if flying off into the distance using either a simple set of two position keyframes or that combined with two scale keyframes, the acceleration always moves from slow at the beginning to progressively faster at the end. Realistically, however, it should be the opposite. The object should move quickly when in close perspective and grow progressively slower as it moves away from the camera.

It strikes me there must be a simple fix for this, but I've yet to discover how. Can anyone help? Thanks in advance.

 Re: Acceleration problem with Position Keyframeson Nov 17, 2015 at 4:59:13 pm

You should change the keyframe influence, either numericaly by goind to Animation -> keyframe velocity...

or visually through the curves editor.

Cassius Marques
http://www.zapfilmes.com

 Re: Acceleration problem with Position Keyframeson Nov 18, 2015 at 1:02:17 am

That sounds like a good solid method, as well. My thanks!

 Re: Acceleration problem with Position Keyframeson Nov 17, 2015 at 9:44:06 pm

Making the layer 3D and adding a camera would be my answer. Then you don't need to scale it but move it in space and the camera perspective will take care of the rest.

 Re: Acceleration problem with Position Keyframeson Nov 18, 2015 at 1:00:38 am

Interesting approach! I'll definitely try it. Many thanks!

 Re: Acceleration problem with Position Keyframeson Nov 18, 2015 at 2:08:45 am

Okay, I've tried the 3D layer and camera...and fear I must be too much of a simpleton to grasp the concept. When I turn the layer into 3D and right click on the layer itself, I get a drop down with Camera showing just above Pre-compose.

Selecting Camera, the choices are:

Create Stereo 3D Rig (an unwanted simulation of 3D glasses)
Create Null Object (grayed out and don't work)
Link Focus Distance to Point of Interest (grayed out and don't work)
Set Focus Distance to Layer (ask for a second layer)

The Camera Tool itself seems to have no effect, though I'm sure it's because I'm doing something wrong. Sorry to be such a newbie. Hope you'll be gracious enough to clarify. Thanks again!

 Re: Acceleration problem with Position Keyframeson Nov 18, 2015 at 7:33:30 amLast Edited By Kalle Kannisto on Nov 18, 2015 at 7:35:19 am

To create a camera, select layer>New..>Camera. Select 35 mm (for instance). Now you'll be looking at any 3D layer through the camera, while every 2D layer in the same comp will not be affected by it.

If you look at your 3D layer position value, there is a z value in addition to the x and y. So, when you move something in space along the z axis, it will move closer and further away from the camera. (This is the case with the initial view. If you move the camera around, and especially if you rotate it, the axis that will make the object go further away or closer to the camera will change.)

So, let's say you want the object to fly in from the bottom left corner toward the center. If you drag the object on the x and y axis to the corner and then drag the z value to a minus range, the object will come closer to the camera and out of the frame. You can put your beginning position keyframe there. Then move forward in time and change the z axis position value only to a large positive number, say 10000 (keyframe). Now when you preview this, the object will fly in like it would in "real life" rapidly past the 3D camera and slowing down into distance in real perspective.

You don't have to have a moving camera to utilize the 3D properties in AE. You just need some 3D layers and a camera. AND you can have 2D layers in the same comp, so if you have a background (footage or image) that you don't want to be affected by the camera, leave the layer 2D.

Obviously there is much more to this, but that's the basic concept.