Fractal Noise / Displacement map... loop STOPS after a few seconds of animation in After Effects

Report · Nov 17, 2020

I am working on a collection of music videos. I have created computer animated visual images in After Effects, like waves of water created with "fractal noise" and "displacement maps." According to the tutorials I am watching, I use "expressions" like +time*150 or +time*200 to animate the fractal noise. At first it looked like everything was working, but the fractile noise stopped moving after a few minues. (The water literally FROZE about four minutes into my nine minute video.) I tried increasing and decreasing the numbers, like +time*2000 and even +time*20000. Nothing worked. I deleted the expression and tried animating with key frames. When that didn't work I deleted the key frasmes and went back to the original expression +time*200. Finally I "rendered" the video in Premiere, thingking maybe it only appeaered to stop becuse I was watching a "preview." One I finished rendering, now it only last 16 seconds? Does anyone have any idea what I'm doing wrong? Everything I try only seems to make it worse, and I'm doing exactly what the tutorials are telling me to do. However, my videos are anywhere from nine to seventeen minutes long. The "fake water" has to keep flowing for the entire video, and the lights of the city need to keep twinkling. I'm almost done with the entire project. The only thing holding me back are these displacement maps.

Report · Nov 17, 2020

32000/150 = ~213/60 = ~3,55

Welcome to the world of computer math! Most property values use 16bit integer precision, which caps off at 32000 and effectively this means that after 213 seconds or 3.55 minutes there are no more unique discrete values left. This is regardless of whether you use expressions or keyframes. It's a hard limit and naturally using even larger values will deplete the pool even faster. Ergo, if you need longer durations you have to duplicate layers to keep them animating. In case of expressions you would then have to subtract the inPoint time to "reset" the start value to zero.

Mylenium

Report · Nov 18, 2020

Hi Mylenium! Thanks for taking the time to respond, and so quickly! Just like you said, when I tried larger values it stopped even faster. If I must duplicate layers, I will. However, I just wanted to share this video with you. Someone on Youtube had the same problem and found a formula that allowed it to loop endlessly without duplicating layers. Here's a link ... https://www.youtube.com/watch?v=8I5EcKhWX0M ... It may not work, and, to be totally honest, it might just be easier to simply duplicate the layers, like you said, but it might come in handy for future projects? Thanks again! I probably will just end up duplicating layers.

Report · Nov 18, 2020

Avoid running out of values by looping the evolution. Do that and it will run forever. Set 2 keyframes at least 1 revolution apart and add loopOut(). Then turn on Cycle Evolutions and set the value for the number of loops. All you have to do is match the number of loops with the value in the second keyframe. Control the speed by the distance between keyframes.