Looping Conveyor belt style in After Effects

[Maria5FE8]

Hello! I am currently trying to animate a continuous loop of boxes going across the screen. Is there any way to do this without having to just create a ton of boxes and animate their position across the screen? Is there an expression I can use?

There are going to be 3 different boxes but those 3 will be continuously moving across the screen. I'm attaching a video to show what I am talking about. The boxes with the same color will be the same.

Also, I'm making it into a gif so I'm trying to keep the size lower. 

Thanks in advance!

[Jose Panadero]

You can use the Offset effect, located in the Distort category. This way you can precompose some items and repeat that horizontal movement with a couple of keyframes.

[Rick Gerard]

To make a perfect loop the first and last frame must be identical and then you just all loopOut() and you're done. 

If it takes 5 boxes to fill your screen then you need a total of seven boxes. Then all you have to do is know the distance total distance between the left edge of the first box and the right edge of the last box. In this case, the distance was 3000 pixels because I created a 400 X 400 box using the rectangle tool and then duplicated it 6 times and offset each box by 500 pixels. I then alternated the colors, grouped the rectangles, and set two keyframes for group position, the second one 1500 pixels more than the first. There's not much to it and it only took 1 shape layer.

If you want the boxes to start off-screen just duplicate the group, get rid of the keyframes on one of the groups, move the keyframes on the second group down a few frames, then animate the first group to the same position as the second group and add an opacity animation to the group to turn it off one frame before it gets to the first keyframe of the second group using hold keyframes for group opacity. All you have to do is space out the keyframes so the speed is the same. Simple, one layer, two groups, and a total of 14 rectangles. It looks like this:

And here's the project file.

Offset only works if your 3 repeating boxes fill the frame. 

[Maria5FE8]

Thank you Rick! I do have a couple questions.

Would this still work if the boxes were png files? Since I can't make them into one shape layer?

Do you happen to know if this tactic would take less to render and have a smaller mp4 file than it would if I just made a bunch of boxes and animated their position across the screen?

[Rick Gerard]

All you have to do is pre-compose the PNG layers and then animate the position of the pre-comp. The same technique applies. You just have to have enough copies of the PNG layers so you can have identical first and last frames and the loop will work.

It's a lot less work and it will render faster than a whole string of duplicate images because once the frames that make up the first loop have been rendered the calculations are all complete. If your comp is 30 seconds long and the first loop repeats at 5 seconds, and it takes 20 seconds to render the first loop, the entire comp will render in about 45 seconds. If you put together a string of duplicate layers the comp would take 6 X 20 seconds or two minutes to render.

[OussK]

if you looking to make a GIF animation, I don't think you need any expression, just be sure your first frame and last frame are exactly the same, and your work is exactly as your keyframes distance, check the attached project file. 

Download - Project File