The composition shown in this screenshot is the one that made up the road. This was made up of a 700x3000 pixel, wrinkled paper texture, stained to look like grass, which looped continuously.
To get it to loop continuously a simple expression was added to the keyframes, which moved the texture, telling them to be looped, even after exiting them.
With the road positioned, it was time to create the null object. A null object is invisible, but can have objects parented to it. These would be the elements which I wanted to make move towards the camera.
To make the null object, which I named "z-ref", move along the Z-axis in my scene, I applied an expression to its position property.
The expression reads:
value-[0,0,(800*time)]
As I understand, this sets the VALUE of POSITION to make X=0, Y=0 and Z=(time multiplied by 800). X and Y are 0, because the null is centered on the scene. Z is told to increase 800 times a second, therefore the speed of the null (and the objects parented to it) can be altered by changing this value!
Last, but not least, this screenshot shows the most complicated of expressions, which weren't covered in the tutorial. I formed this from research using the After Effects, online documentation.
In simple:
I needed a way to offset the elements which were parented to the null, from the null, otherwise everything would've been stuck to it as if it were a magnet.
In the end, I found I could apply an "effect" called 'Slider Control' to the layers I needed to offset, and then use the value of it in an expression to set the distance (in pixels) that it would have from the null.
The above screenshot shows an example of two trees that aren't parallel with each other, this is because I have offset one of them by 525 pixels, shown in the top, left-hand panel. Although I didn't offset separate trees like this in the final piece, but rather pairs of, this is the method I used to create a make them approached one after the next.
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