One of the main things for people who use other compositing software and then spend a nuke is the question of how to work with simple expressions but very useful as wiggle or time, In nuke program parameters change but basically the same operation, now explain the random expression which is used to create automatic animation within a range of values which can be very useful when creating a fractal noise effects like glows among others.
1. place a node such as noise
2. then modify its parameters for more complex noise
3. parameter on which we will focus for the creation of noise the "Zoffset" (but may do so in any of them)
4. in the numerical parameters we click and add expression
5. it write the expression "random ()" that generates an animation we already random values, but let's polish, as you will realize handled values less than 1 (in some cases depends on the parameter), we multiply this expression by any value in this case 10 with this increase the range that has the expression to vary numerically.
6. will realize that the noise is automatically animated but the change is very fast (see the curve editor), to smooth the movement and make it look more fluid add the following (+ frame / 5) which will make each box go smoothing interpolation curve and in turn
7. As we see in the animation interpolation looks much better, the animation is more fluid (obviously the values should be modified according to your needs)
8. Now we create an expression control what we do is create a slider to thereby have greater control over the expression
9. node options on right click and select press manager user knobs.
10. added a floating point slider and we name such as "control_noise" and we create and minimum and maximum values
$11. Now we just have to make the control handle which the expression for going to the expression we previously created and add * (name of the control) or in this case
Our final expression