3D Space // 13
to see it): A popup menu appears with a list of alternative views. Select Top or Left, and scrub the Z Positions of the wheels to see how they move. Note that from these views, you can tell that all three wheels are still the same size. Select Custom View 3 (which gives you an angled perspective) and scrub all three Position axis values for the wheels. Once you feel you have a good grasp of the Z axis, return to the Active Camera view; we will explore these alternate views in greater detail later.
Taking a Spin in 3D Now that you’ve got the hang of moving objects in 3D, let’s move on to rotating them. Open [Ex.02c]; it contains another copy of the now-familiar bike wheel, currently in 2D space. Select it and type R to reveal its Rotation property. Scrub this value; it rotates around its axle as you would expect. Leave this property at some value other than 0°. Enable the 3D Layer switch for this wheel. There are now four Rotation parameters: Orientation, X Rotation, Y Rotation, and Z Rotation. Once you get over your initial shock, you might notice that your previous Rotation value has been copied to the new Z Rotation parameter. Scrub the Z Rotation value, and the wheel will rotate just as it did before. Now play around with scrubbing the X and Y Rotation values. You will notice that each causes the wheel to rotate around its corresponding axis arrow in the Comp panel. You will also quickly notice that rotating these axes ± 90° results in the wheel disappearing as it is rotated on edge. As we mentioned earlier, 3D layers have no thickness. Accidentally rotating a layer on edge and causing it to disappear is one of the most common “mistakes” when you’re working in 3D in After Effects. Keep rotating past 90°, and you will see the back of the layer, which is a copy of the front – but it’s backward now, as you have flipped it around. Return to [Ex.02b], select all three layers, and press R to reveal their Rotation properties. With all three layers still selected, enter a Y Rotation value of 90° for one of the layers (they should all jump to this value). Notice that only the layer that was deadcenter – wheel 2 – disappears on edge; you can still see slivers of the other wheels. This is another manifestation of perspective. Select wheel 1 or wheel 3, type Shift+P to also view its Position, and scrub its Z Position value, noting how you see more of the “side” of the layer as it moves closer to you.
The three Custom Views offer a quick way to view a scene from different perspectives, without having to create a camera first.
3D layers have four – count ’em, four – Rotation parameters: Orientation, X Rotation, Y Rotation, and Z Rotation (this last value being the same as 2D Rotation). This may seem like overkill, but each has its purpose.
[Ex.02b]: Although all three wheel layers have been rotated “on edge” (90° around their Y axis), you can still see slivers of the layers that are not centered in the view. This is another example of how 3D perspective alters how layers are seen.
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