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Random/Wiggle questions
Hi
I’m new to expressions and just learning about the massive power in reducing edit time on it. Enjoying it, but have 3 questions I can’t find internet answers to, or they’re hidden in a mountain of jargon and I didn’t realise I found them.
1: I wanted to create an effect of having a flicker-type effect on exposure in a shot, so that the exposure especially on brighter areas go brighter and dimmer randomly, not too much and not too fast, but frequently enough to work with fast paced music or rhythm.
My idea went to adding Exposure and burning the bright spots a little bit, then adding a glow and putting a random expression on the glow intensity. unfortunately, it created more of a strobe effect that went way too fast, and I wanted to see if I could control the speed with which the random jumps, so it’s not so fast. I guess that’s the definition of random, but what do I do?2: Same idea as above took me down a different path of though. Instead of the random, I tried a wiggle but soon realised that the wiggle goes into negative exposure too in terms of amplitude, which means my shot not only gets brighter, but also goes completely black. Is there a way to curb the range in which the wiggle wiggles? I know you set the max amplitude, but what about setting a minimum?
3: Different attempt. I wanted to add random distortion on a shot, and went for a Bezier Warp. On the Left top Vertex I put a random expression on the value with the parameters I wanted, and it worked well.
Jumping to the Right Top Vertex, I tried the same. my random was something like: random([1024,1060],[-25,10]), but instead of staying within those parameters, the Vertex jumped straight down to the bottom left corner and made the whole thing look really silly.
Am I doing something wrong? I wrote the expression the same for the Left top Vertex and it did what I wanted.I hope these aren’t too silly, but I have to know the answers. Thanks for your help!
Mario
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3 Replies
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I would constrain thetopleft vertex between something like [0,0] and [source.width/2,source.height/2]
the top right between [source.width/2 , 0] and [source.width, source.height/2] etc.
in effect, constraining each vertex to it\’s \”natural\” quadrant so it never gets folded into a unintuitive polygon.
Makes sense ?with regards to only wiggling values that are higher than the current value.
Math.max(value , wiggle(1,2) );
This will clip off negative exposures,
or:
wiggle(1,0.5). + 0.5;
wich also never does a negative exposure, but the average of all values will be +.5, and a +0 exposure will seldomly occur.
Try both and see which u prefer.
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Flippen hell. I feel like I know 0.0000001% of after effects looking at expressions and what some of you guys in these forums know.
Thanks for that. I’ll give them all a shot and see what works.
Mario
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Flip,
How do you control the speed on a random? is there a way, or does it literally just go random as it feels like it, meaning speed of the expression on, say, opacity is controlled with a different script?
Ideally, I’d like to have the random opacity happen at once every 2.5 seconds.
Similar line – can a wiggle be applied to a frequency slower than once per second?
Thanks for your help
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