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sine wave driving RGBA value trouble
//generate wave red = Math.sin(time*10); //normalise to 0 - 155 rednorm = linear(red,-1,1,0,255); //rgba array [rednorm,255,255,255];
Hi,
Im having a little trouble with getting the RGBA values of a ‘fill’ effect to be controlled by a sine wave..I was hoping for the R value to peridically ramp from 0 to 255 smoothly, creating a smooth change in colour over time. (see my code below).
Instead my fill colour stays white and flickers on cyan for a split second then goes straight back to white, with no smooth graduation in colour.
Can’t get my head around why this shouldn’t work, but I am a newb to expressions so please excuse me!
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6 Replies
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Hi John,
The colors are expressed with 1 as maximum, not 255. So just change the code and it should work.
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Do you know why that is Filip? I encountered the same problem a week ago, trying to make a levels effect flash and eventually realised the input white had to be 0~1 not 0~255 like it says.
It’s most confusing, I’m just wondering if there’s any logic behind it.
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Only in after effects do children get to pick and whip their parents.
https://hennell-online.co.uk -
It’s just a convention I guess.
Though from a programming perspective it does make sense: 0= off (black), 1=on (white).
The accuracy with which you express inbetween values is arbitrary, 8 bits, 16 bits, 32 bits.What would happen if you work in 16 bits per channel, should you rewrite all your expressions to work with a maximum of 65535 ?
You can choose to express all colors in After Effects as in the range 0-1 by setting the viewing preferences in the info palette.
In 32 bpc mode, this is the standard way of expressing values, because values can also go below 0 and above 1. It’s easier to understand that 1.5 is 50% super-white than thinking what the hell a value of 21384161439 is 😉
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Thank you all!
I’ll try that when I get home. The was indeed very simple. It seems like it makes sense using 0 – 1 instead of 0 – 255, for the reasons you mentioned. Also, in this case, I can leave out the normalise line of code now.
Thanks
John -
Hadn’t thought of the advantages it brings to colour modes, it makes good sense when you explain that.
Still, sensible though it may be, It could be more user friendly – you expect expressions to have to return the same value as the default option not something completely different…
Thanks for the info though, always good to understand what’s going on.
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Only in after effects do children get to pick and whip their parents.
https://hennell-online.co.uk -
You’ll still need the normalize, as negative values won’t make any sense.
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