In the previous three posts, we took a look at the internal workings of real cameras and their counterparts in the After Effects virtual cameras. We now shift our focus to the external workings of camera movements and how to achieve those same results in After Effects. In part four, we will examine how to use the Orbit Null to achieve more predictable results when looking at a static or moving subject.
Creating a Camera Orbit null is very easy. Create a camera in the comp, and select Layer>Camera>Create Orbit Null in the menu bar. That will create a new null object, and parent the camera to the null object. This means that any transform property changes that you make directly to the camera will be made relative to the null object, NOT relative to the 3D world in which the camera exists. On the other hand, any changes that you make the the null object WILL be relative to the 3D world. Additionally, the cameras point of interest will always be the null object, and any movement that you make directly to the camera will result in a reorientation of the camera toward the null object. This may not always be desirable. There are times when you want to have a dolly effect on the camera without reorienting the camera toward a specific point. In that case, 3D camera nulls are NOT the solution in your project. On the other hand, if you are orbiting the camera around a moving object, and want to have an easy means of doing so, then the Camera Orbit Null may be just the trick for you!
Controlling the position and rotation values of the null object affects the camera. Do you want to spin the camera around your subject? Then change the rotation values of the null object. Do you want the camera to move with the subject (if the subject is moving)? Then alter the position values of the orbit null, or add an expression linking the position values of your subject to the position values of the orbit null. If you wish to change the distance of the camera relative to the orbit null however, you’ll need to change the position value of the camera itself. Usually this will involve changing the z-position value to move the camera closer or further away from the null, but it is possible to move the camera to the left or right if you choose. You can also control the camera settings as we have learned previously. Parenting the camera to the orbit null will not change their operation in any way.
By way of example, consider the following “scene”:
Set-up – No expressions and a stationary camera.
The white rectangle moves forward and to the right, orienting itself along its motion path (this was done using the “orient to path” option in the auto-orient dialogue box). The camera and the orbit null remain stationary, with the camera raised slightly so that we can see the motion of the rectagle. This will serve as the basis for further explanations.
If you want the orbit null (and thus the camera) to follow the object, then open the position property of both the orbit null and the white rectangle and expression pickwhip the position value of the white rectangle to the orbit null. You will see the following…
Example #1 – Position Linked
If you want to set up the camera to be a “chase camera”, then use the expression found here (credit to Dan Ebberts or Motionscript.com) in the orientation value of your Orbit Null. Assuming that the subject of your camera is auto-oriented along its motion path, then that expression will link the orientation of the orbit null to the subject.
Example #2 – Position and Orientation Linked
From there, you can animate the camera however you wish.
Example #3 – Position and Orientation Linked, Orbit Null rotation animated to make camera swing around subject
(Note: It is not necessary to link the orientation in order to swing the camera around your subject.)
There are MANY other ways to use orbit nulls, but hopefully this explanation helps you to come up with some creative ideas of your own!