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Final Cut Pro Quick Tip #39Understanding the Anchor Point
What is an Anchor Point?
In most applications, the Anchor Point is the geographic center of the layer. Being positioned in the center of the layer means all action takes place around this point.
Before showing some ways in which the Anchor Point can help you, I really need to point out how different applications map the Anchor Point. In an application like Adobe After Effects a 720x480 video layer would have an Anchor Point residing at 360x240. In this instance, After Effects begins measuring pixels from the upper left hand corner of the layer, so the center of the layer is 360 pixels over and 240 pixels down. Final Cut Pro, on the other hand, begins at the center of the layer and works out with the center of the layer residing at (0,0).
This is more along the lines of traditional math, where you start at the origin. If you move to the right on the X-axis you are moving in a positive direction, and if you move left on the X-axis you are moving in a negative direction.
So in After Effects the upper left hand corner of your layer would be (0,0), while in Final Cut Pro it would be (-320, 240). This is an important concept to keep in mind as you are working with Final Cut Pro. If you wish to move your Anchor Point to the left side of the layer, you will be working with negative values.
How can you change the Anchor Point in Final Cut Pro?
The Anchor Point information is located in the Motion Tab in the Viewer Window. You will notice that there are actually two controls Center and Anchor Point. While you may think they are the same, they actually work differently from one another.
The Center Point determines where the video layer is positioned on the screen, while the Anchor Point is used more for the rotation and scaling of they layer. I think Apple would have been better to change the Center Point to Position to avoid some of the confusion.
In order to change the Anchor Point of the video layer, simply enter the coordinate value in the X and Y axis Box. For example, if we wished to move the Anchor Point to the left edge of the layer, a value of (-320, 0) would be entered.
Notice that the layer has not moved at all, and if you are not making any other changes to the layer, moving the Anchor Point would be useless.
Making the Anchor Point work.
?So what happens once the anchor point has been moved? Ah, very good question. To answer it, lets take a look at layer rotation.
When the Anchor Point is located at (0,0) and we change the rotation of a layer, notice how the layer spins about its center.
As the Anchor Point moves to one side of the layer (-320,0), the layer now rotates from the edge.
Another way we can see the Anchor Point in action is to take a look at the effects of scaling a layer.
With the Anchor Point located at (0,0) scaling occurs from the center.
But lets imagine a scenario where you wanted your full screen image to shrink and move to the corner of the screen to create a pseudo picture in picture effect. By leaving the Anchor Point in the center of the layer, you would first have to scale the layer, and then position the layer in the new location. If you were animating this effect using keyframes you would end up with four different keyframes (two for Scale and two for Center).
However, if you moved the Anchor Point to the lower corner of the layer (360, 240), and then scaled the layer, look what happens.
In this case, Final Cut Pro is shrinking the layer based on the location of the Anchor Point and because the Anchor Point resides in the lower right hand corner of the screen, you get the effect of a position effect as well. Now you end up with only two keyframes and also save yourself the insanity of trying to get the center and scale animations to line up.
Experiment with Final Cut Pros Anchor Point and see how making one minor change can improve the quality of your motion elements.
For a complete list of all the Final Cut Pro Quick Tips to date, visit my website at www.mindspring.com/~schleicher.
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