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Fractal Noise – Offset & Rotate
Hi. First of all let me say that I am new here and my English may not be the best, so please bear with me…
OK, here’s the problem:
I have 2 points (“Start” & “End”) with coordinates [X1, Y1] and [X2, Y2] + a layer with Fractal Noise. In Fractal Noise I want the Offset Turbulence to follow the starting point (which is easy), but aslo move certain distance in Start-to-End direction each frame.
For that moving factor I’ve got this:
speed = percentage/100; // Let’s say 0.25
So every frame it would offset by (X1 – X2)*0.25 in X axis and by (Y1 – Y2)*0.25 in Y axis. But still linked to the position of “Start”.In some early tests I tried putting
effect(“Fractal Noise”)(“Offset Turbulence”).valueAtTime(time – thisComp.frameDuration);
in a Point Control and reusing it in the main expression, but it’s just pointing at the “pre-expressioned” value of the Offset Turbulence.I know that expressions have no memory of their previous values, so that’s why I’m asking – is it it even possible?
Just to clarify it a little bit – I am looking for something similar to “Lock Noise to Saber” feature in the Saber plug-in by Video Copilot. So ideally, the rotation should also vary, which I already kind of figured out:
if (X1 – X2 < 0){
Math.atan((Y1 – Y2)/(X1 – X2))*(180/Math.PI)
}else{
Math.atan((Y1 – Y2)/(X1 – X2))*(180/Math.PI) + 180
}
… but since Fractal Noise has no Anchor Point (it’s rotating around that Offset point instead of the the “Start” point), it would make everything so much more complicated that for now I’m just focusing on the Offset Turbulence (but if you’ve got any ideas, I would appreciate it).I hope I’ve described it well enough, otherwise just ask me and I’ll try to clear everything up.
Thank you in advance for any help, Vladislav.
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6 Replies
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Something like this probably:
perFramePct = .25;
p1 = thisComp.layer(“Start”).transform.position;
p2 = thisComp.layer(“End”).transform.position;
deltaF = timeToFrames(time)-timeToFrames(inPoint);
fromComp(p1 + (p2 – p1)*deltaF*perFramePct);The perFramePct seems high–it only takes 4 frames to go from Start to End.
Dan
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Wow! It works just perfectly. And also – Dan Ebberts himself!
Seriously, thank you.
OK, final question. How would you make it so that its rotation is aligned with those points? Sorry, I don’t know how to put it… If you imagine every point on the Start-End segment and the “End” point moves within couple of frames, all those imaginary points would be further away from “Start” (which now works), but they would also rotate around the “Start” point, so they are still on the Start-End line. I hope it makes sense like that.
Maybe I could just use the Fractal Noise effect on a bigger solid and rotate it using classic transform options, but I don’t know – it sounds a little bit clumsy. Any advice?
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I think I’d need to see a sketch or something.
Dan
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All right, here’s a picture of how it should work:
a and b are just random imaginary points on the Start-End line in Fractal Noise, alpha is the angle driven by this expression I mentioned before:
if (X1 - X2 < 0){
Math.atan((Y1 - Y2)/(X1 - X2))*(180/Math.PI)
}else{
Math.atan((Y1 - Y2)/(X1 - X2))*(180/Math.PI) + 180
}
Vladislav -
Try this:
p1 = thisComp.layer(“Start”).transform.position;
p2 = thisComp.layer(“End”).transform.position;
v = p2-p1;
radiansToDegrees(Math.atan2(v[1],v[0]))Dan
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Well, it works OK but when I put it in Rotation in Fractal Noise, it still rotates around the Offset point instead of the “Start” – so when I mess with “Start” and “End” locations, it occasionally moves backwards…
Vladislav
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