Particles, Nulls, and Trim Paths

Null Objects and Particles

We covered a lot of ground in our VFX class, including particles, Motion Sketch Panel, Trim Paths, and utilising Null Objects to achieve really cool effects.

Firstly, we quickly learned how to control particles using Null Objects. We needed to create a new composition and add a new solid shape. While that was selected, we would add the particle effect to that layer. Then, we added the necessary Null Object – we needed to click on P (to bring up the Null Object’s position rather than digging through to find it), then alt-click on the clock, and add an expression on for wiggle.

After that, we go through to find Effects > Particle Systems II > Producer > Position to then alt-click on the clock next to that so we can make the Producer’s position a child of the Null Object’s position. At this point, the composition looked as follows:


Finally, it was just down to changing the solid shape’s blending mode to Add and then fiddling with the particle system to achieve the desired result!


Although it’s a bit messy, I circled the items that we changed to make the “firework” particle effect look more like a line.

The line would be randomised because of the wiggle, but this would be a view into what we would do further in the class.

I liked the look of it, though. I think this sort of particle system manipulation and usage can achieve a really awesome-looking result. Of course, the Painting With Light videos were brought up again, since we’ll be starting work on that project next week, and this sort of activity reminds me a lot of that.



The first GIF above was the result of what I just outlined, but the second one was done through duplicating the path and changing the offset. I then just changed the colour of the second line, so that it was more visible, but you could add as many lines as you want just by continuously duplicating.

Motion Sketch Panel

Following this, we were shown how we could manually create a path using the Motion Sketch Panel and then attach a particle effect to it. First, we had to create a Null Object and then go to the Motion Sketch Panel.


If the Motion Sketch Panel can’t be viewed on the right hand side, it can be added by going to Window and finding it in the drop-down menu.

We changed the settings for the smoothing from 1 (which would be very sharp), to 10 (which would be a bit more lenient on the line).

After that, we could click on the start button and the sketch would start recording once you clicked down on the canvas. I ended up writing my name in cursive, just to see how it would turn out.


Pen Tool and Trim Paths

We finished off the class by starting a new project/composition and importing a reference image of the word emitter. Using the pen tool, and (very important!) not have any layers selected, we were going to trace out the word so that we could have the particles follow the line using Trim Paths.

Although it might be a bit hard to see, we needed to add the Trim Path to the newly created Shape Layer by clicking on the small arrow next to the Add, which can be found to the right of the line that has Contents on it. Starting at the very beginning of the composition, we needed to set the End percentage to 0, then move our timeline on 8-10 seconds in to put it back up to 100%.


The result is very neat, but it could be made better!

Instead of using the pen tool to create a new shape layer, we needed to add a solid object (and we changed the opacity to about 25% so we could see the original guide underneath) which we could create a shape mask with – this needed to closely match the original pen tool trace above. Once again, with the pen tool it was a bit finicky to get the writing nice and look the same, but I think my work was near enough to get away with.


After that, it was a matter of adding another Null Object so we could copy and paste the Mask Path to the Null’s position.


I needed to alt-click on the end of the path (the blue dots in the timeline above) to stretch them out so they were the same length as my original trim path (10 seconds). Below is what the Null Object’s path looked like afterwards.


Finally, it was just down to adding the particle system (like before) to a solid and parenting it to the null, so that we could fiddle with the settings and get something that we liked the look of. I think mine turned out quite well – it sort of reminds me of drawing with a sparkler, while I managed to get the writing to look sort of neon.


Unfortunately, we didn’t quite have enough time to looking into the last part of the lesson, which was meant to be controlling lens flares with nulls and expressions, but we’re supposed to pick this all up in our nest lesson. I’m looking forward to it, since I really enjoy playing around with the particle system in After Effects!

Posted in VFX

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