Newb - smooth scrolling credits in AE ?

Question

I am doing an intro title sequence for someone.
It consists of about three separate scrolling credits.    The scroll from bottom to top.
I have done the text in Photoshop and imported it into AE.
My problem is the text appears jerky as it scrolls up.
Is there anyway to get AE to give me the smoothest scroll possible ?

Answer 1

If you are using the expression that I posted above all you do is set the speed to a whole number. DO NOT USE fractions.
The stutter your talking about can be caused by a bunch of factors. There's something called a seven second rule and a bunch of other info available HERE. Read both articles in this FAQ.
To change the expression to scroll horizontally just flip the values to the other parts of the array.
Expression for horizontal movement instead of vertical:
t = time;
fr = t/thisComp.frameDuration;
y = value [1];
s = 4; //Speed in pixels per frame must be a whole number
x = value[0] - (fr * s);
[x, y]
This expression gives you a little more freedom because you can position the layer anywhere you like in the comp and it will start crawling right to left.
To change the direction simply change the minus sign in the x method to a plus. To change this expression to a roll swithch the methods for x and y so Y is modified by time.
Let me explain the expression. the value[0] and value[1] declarations simply call up the original values of X and Y. The math is simple. We take time and divide it by duration of a single frame to give us a frame count in whole numbers. Then we subtract the frame number multiplied by the number of pixels we want to move from the original position. It's easy as pie.
I hope this helps.
Judder can be caused by an interaction with the refresh rate of your screen and the frame rate, from the frame rate and the movement, or from playback errors using mpeg compression. It's a bugger for some motion. Horizontal and vertical movement of hard edges like you get from text can be extremely problematic.