Nuke: blip expressions to copy and paste

Using waves to drive animation in Nuke – part 2

In my previous article on this subject I gave some examples of expressions that you can just copy and paste into any value in Nuke to quickly create an infinitely repeating animating pattern. I was asked in the comments how to do a ‘blink expression every x frames’. I answered with ‘just use the square wave example’, but I realised that’s not what he was after. In this article I’ll give you some expressions that can be used for such a blink or ‘blip’ animation curve.

I have also made a new version of my gizmo WaveMaker that incorporates all of this, so you can download that if you’d prefer. It’s now in .nk format rather than .gizmo so it’s easier to share.

Square on/off blip every n frames

(((((sin(((frame*(pi*2/(freq/2))/2)+offset))+1)/2)) > cutoff ? 1 : 0) * (maxVal-minVal) ) + minVal

(Where ‘freq’ is the number of frames between blips, ‘offset’ is the time offset, ‘cutoff’ is a value between 0 and 1 which controls the width of each blip, ‘minVal’ is the lower value, ‘maxVal’ is the upper value. As in the previous article, either replace these variable names with your values, or better still, create a NoOp node, add some user knobs with those names and you’ll be able to adjust it on the fly)

Simpler version: ((( sin( ( ( frame * ( pi * 2 / ( 5 / 2 ) ) / 2 ) + 0.5 ) ) + 1 ) / 2 ) ) > 0.95 ? 1 : 0

(Blip pattern between 0 and 1, replace the ‘5’ to adjust amount of frames between blips, adjust the ‘0.5’ to move the whole thing back and forth in time, and adjust the ‘0.95’ to adjust the width of the blips)

So what’s it doing?

It’s really just a simple sine wave with another expression applied to see when that sine wave goes above the cutoff point. If so, set the value to 1, if not, set it to zero. If a high enough cutoff point is given (like 0.95) most of the time the sine wave will be below that value and only at the very tip of the peak go above it. The lower the cutoff, the longer the peak rises above the cutoff point and so the blip gets wider.

But if you need something a bit smoother than a simple on/off, I’ve also made this version:

Smooth pulse-like blip every n frames

(min((max((((((sin(((frame*(pi*2/(freq/2))/2)+offset))+1)/2)) > cutoff ? (((sin(((frame*(pi*2/(freq/2))/2)+offset))+1)/2)) : 0)) – cutoff,0) * (1/(1-cutoff)) * 1.001),1) * (maxVal-minVal) ) + minVal

Slightly simpler version: (min( (max( ((((( sin( (( frame*( pi * 2 / ( 10 / 2 ) ) / 2 ) + 1.55 )) + 1 ) / 2 )) > 0.7 ? (((sin( ( (frame * ( pi * 2 / ( 10 / 2 ) ) / 2 ) + 1.55 ) ) + 1 ) / 2 )) : 0 )) – 0.7 , 0 ) * ( 1 / ( 1 – 0.7 )) * 1.001) , 1 ))

(Smooth blip pattern between 0 and 1, replace the ’10’s to adjust amount of frames between blips, adjust the ‘1.55’s to move the whole thing back and forth in time, and adjust the ‘0.7’s to adjust the width of the blips)

Multiple blips

To make a complex repeating pattern of blips, create several user knobs using the above expressions, set to different values, then in another user knob max them all together:

max( max( blip1, blip2 ) , blip3 )

Manual looping

Remember, if you just need a quick repeating pattern for one thing in one shot, then building all these expressions is probably overkill because you can just draw a pattern in the curve editor, then tell Nuke to loop that pattern. This is more for the cases where you may have several things blinking on and off at different rates (perhaps a HUD, graphics display or warning lights on buildings), and you may need to go and adjust them all later. I personally wouldn’t go to the trouble of building all the knobs each time, that’s why I built BlipMaker into my WaveMaker gizmo so it’s available whenever I need it. My article where I took all my expressions from WaveMaker and made them available for quick copying and pasting has proved rather popular though so I thought I’d do the same for BlipMaker.

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WaveMaker v4

WaveMaker v4 available

 

Edit on 12/10/2013: This tool has been superceded by my new tool Animation Maker.

If you are familiar with my gizmo WaveMaker, I have made another version with two differences:

1) BlipMaker added. Allows you to generate blip animations for animating flashing beacons, LED lights or anything that needs to blip on for a frame or so every few seconds. WaveMaker itself can’t generate such a curve, it can only create squared versions of existing waves, meaning you could get it to come on for a frame, but it would only be off for another frame before it came on again. BlipMaker lets you choose the ‘on’ length and ‘off’ length separately. Examples below.

2) Instead of sharing the gizmo, I have provided a .nk file with a group node inside. If you want to use it as a gizmo, just load up the file, load the group in the properties tab, and Export as Gizmo… from the Node tab. However if you want to avoid problems when sharing your scripts, you can just import this .nk file into your script whenever you need it. The third, best option is to use the provided example menu.py file to create a custom button in your toolbar that looks and behaves like a regualar gizmo but is in fact just importing that .nk file each time you press it.

Download the zip file here

BlipMaker

Example curve: Blip of one frame, every 24 frames

Example curve: Soft blip over three frames, every 24 frames

Example curve: Three one frame blips, every 24 frames

Example curve: Combination pattern of blips with different settings, every 24 frames

These are just a few examples, you can play around with the sliders to get all sorts of combinations. Feel free to drop me a line or leave a comment if you use WaveMaker in any of your projects, I’m always interested to see how people use it.

If you just need to grab these expressions quickly, have a look this article where I break it down further.