Help, I got jittering line grid animation in After Effects

[jinx_7393]

I just finished creating my animation in After Effects, but I got jittering line animation. I already tried to fix it by increasing the frame rate, adding a noise effect, increasing the bit color from 8bit to 16bit, adding blur, etc., but the problem is still there.

I attached the project file too. I know some assets may be missing, but my main problem is in the grid object.

Please help me!

[Rick Gerard · Accepted solution]

You are running into a problem called judder. It is caused when thin lines move through the pixel grid and anti aliasing changes the color and luminance values by blending the single pixel wide line into two pixels. You have to increase the thickness of the moving horizontal lines to at least one pixel and then make them move a whole number of pixels per frame to get a perfect, no judder, moving horizontal or vertical line.

The solution to this problem is to duplicate your Grid Effect, use one for the horizontal lines and one for the vertical lines so that the vertical lines do not get too thick. That way you can increase the tickness of the moving horizontal lines so that they are never smaller than one pixel wide. Then you apply an expression to the Grid/Anchor Point property that counts frames and multiplies the value by the number of pixels you want the line to move per frame. 

Because your Grid layer is a rotated layer (should be - 90º instead of your 90º setting), the easiest way I can think of to figure out the right speed is to add a Slider Control for Speed to the top of the Effects Stack and include that in the expression. 

I'm working on a version of AE that can't save to your current version so I'll give you some screenshots showing the modified properties of the layers and the expressions I used. You'll also have to add some directional blur to the moving Horizontal lines. This is what worked for me. 

The expression:

// Horizontal Grid Anchor Point
f = timeToFrames();
s = effect("Speed Slider Control")("Slider")/10 + 1;
y = f * s;
[0, -y]

 Here's what the Effects Panel looks like:

Pay attention to the order and the settings.

This is what the timeline looks like:

You zoom into the composition panel to about 400% and adjust the Boarder of the horizontal lines, the speed slider, and the Directional Blur settings until you get a uniform looking line at the top of the grid when you step through the timeline one frame at a time using the Ctrl/Cmnd key + the down arrow.

When you get the grid layer working as it should it might be a good idea to Pre-compose it, moving all attributes to the new comp and if your system has any problems with peviews you might consider the Composition/Pre-render menu. This will replace the layer with a Movie file with an alpha channel.

I've uploaded a video of the Project so you can see the result at 400% 

I hope this helps.