Particles, Nulls & Trim Paths

First VFX lesson of the new year and it seems we would jump both feet first into preparation for the upcoming painting with light exercise. I know I’ve not mentioned much of this before but it has been ticking over in the background. It’s based on Peter’s own adverts for Turner Classic Movies, I could only find one example online which is this.

Much like the original ads Peter wants us to pick a movie, or something visual that has meaning to us or gave us inspiration and create our own version. I’ve still not decided exactly what I’d like to do yet but it’ll probably be Blade Runner related.

The lesson was broken up into three separate exercises.

Controlling particle systems using Nulls

Ah nulls, you never cease to be the most useful thing in AE. We’ve covered particle systems before, but simply their existence, now its time to put them to work and it turns out the easiest way to manipulate them is with Nulls.

I’ll skip the details of making the particles and nulls as that has been covered before. The things worth mentioning is that for some quick animation we added a wiggle expression to the null (wiggle 1,400).


To get the particles to follow the null you have to parent the particle systems producer to the position of the null, not the null itself as I made that mistake.


As seen above these are the settings I changed on the physics and particle tabs.

  • Animation – Direction Normalised
  • Radius XY = 0.1
  • Velocity = 0
  • Transfer Mode = Screen

After duplicating the result and editing the colours this was the end result. Very pretty for what amounts to about two minutes work once you know what you’re doing. Really beginning to see the power of AE.


Following a Motion Sketch Path

We moved on to get a particle system to follow a more advanced path of our choosing, over the randomness of a wiggle expression. AE has a free hand path drawing tool called Motion Sketch, I can imagine this being quite powerful if you had a graphics tablet at hand, with a mouse I drew a series of wavy up and down squiggles to demo the tool.


The sketch options had the path smoothing turned up to 10 from 1, 1 is exactly how you drew it with no smoothing. With the mouse drawn path this would have been very jerky.

Other than that the process to marry this up with the particle system was exactly the same as before, parenting the producer to the null position (motion sketch path was created on a null too).


Pen Tool & Animating with Trim Paths

Here is the big exercise which should be concluded next week. I’ll run through what I have so far.

Here is the prepared file we were all presented with. The aim was to use the pen tool to recreate the emitter text as a path we could use to animate using a trim path (more on that soon).


Using the Pen Tool with no fill we followed the path of the word making sure to keep the whole path as one continuous line. Once this was finished under the newly created shape layer we could click on ‘Add’ under Contents and choose ‘Trim Path’.


Turning the keyframes on for the Trim Paths ‘End’, we added a key for 0% on the first frame and a key for 100% at the end. This automatically animated a reveal for our path, however unlike previous times it now had no fade off.

This path was then duplicated, the stroke increased, gaussian blurred and its colour altered. The two paths together gave a neon effect. Honestly I don’t have any work in progress shots at this stage as I was too busy trying to keep up with the lecture, so bare with me to see everything in the end result.


The next step would be to get a particle system following the trim path as it drew out the words. Going for an effect of them being cut out of the background and the resulting sparks. To do this we had to redraw the path of emitter again as close as possible to the original path on a new solid object.

Now after creating another new solid to assign a particle system to, we would also create a new null, go into the shape layer of the new pen path and copy its mask path to the nulls position. Similar to before but this step is necessary as you cant assign a particle system directly to a pen path/shape layer.

Finally assign a particle system to your second new solid object and then parent its producer to the nulls position. Long winded with many solid objects and nulls but the effect I think is worth it.



Now we were supposed to progress to adding lens flares and further effects but time ran short. I did however with the help of Peter get a little bit closer in preparation for these steps next week by turning the whole scene into a pre-composition. Essentially flattening all layers/effects etc into one object in a new composition.

In doing this you can add effects to the entire vfx/animation. Some duplication of the pre-comp and a few radial blurs later it changed into this.


I look forward to finishing this next week. It had been a great exercise in really seeing how powerful these systems can be in AE, even for beginners. I may not have enrolled on the course with a specific interest in VFX but I do think my interest is growing.


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