Particle group> Streaklet group

Streaklet is a long exposure, light painting effect. The base particle is the Streaklet particle in the Particle Type. There are controlling parameters in the Streaklet subgroup.

At left, the full Streaklet group parameters. At right, the Streaklet option in Particle Type.

Random Seed

Change the look of the streaks simply by changing this parameter.

Left to right, different Random Seed values chosen.

No Streaks

Set the number of streaks. High values make more streaks, which give a more detailed look. Lower values make fewer streaks and give a more simplistic look.

Left to right, No Streaks set low and high.

Streak Size

Set the size of the streaks. Low values gives thinner, more separated streaks. High values give thicker, more overlapping streaks. A value of 0 turns off the streak.

Left to right, Streak Size set low, mid-range and high.

How to create a Streaklet 'iPod effect'

Following is a tutorial to create the Streaklet effect, which you could loosely term the iPod look.

Start with a new comp (Ctrl/Cmd-N). Make the comp 640*480 at 30 fps and 5 seconds long. Add a Solid layer that is comp sized and apply Particular 2.0. Go to Particle> Particle Type and choose Streaklet.

First we need to create a 3D path for the Streaklet to follow. Let's create a composition Point Light and name it 'Emitter'. Set Emitter> Emitter Type to the Light(s) option. Both actions tie into the Options Panel and its Light Emitters> Light Name, where the default name is already set to 'Emitter'.

In your Timeline, select the Emitter and type 'P' for Position. One way to set the Streaklet path is to hand keyframe the X, Y, Z movements of the Position. This is a little labor intensive, so let's instead a simple expression set to wiggle the Position.

If you Option-Click (Alt-click) the stopwatch icon next to the Position name in the Timeline, the Expression area opens. Type in the expression transform.position.wiggle(3,200). This sets the number of wiggles to 3 and sets the length of the wiggle to 200 pixels. Now the Streaklet particles are moving along an interesting path.

Left to right, before and after the wiggler expression.

To make our effect work, we need the particles to stand still. To do this, let's go back to the Emitter group. Set the Velocity, Velocity from Motion, and Emitter Size X, Y Z all to 0. This makes the particles just omit from the light and they stand still from where they were omitted.

We're getting closer now to the Streaklet effect, and also about to stumble into a problem. Particular interpolates each frame linearly. This is great for a slow moving emitter that is going so fast you can't see jaggies. But if you want the emitter to move fast, you need to go to the Emitter> Position Subframe. Change this option to 10x Linear to make the emitter look smoother.

Right now there are gaps between the particles, but the iPod look is a long streak. Still in the Emitter group, let's increase the number of particles with Particle> Particles/sec so those gaps are filled. Be careful not to set the Particles/sec too high since more particles will greatly affect your render time. We'll set the value to 450, which is a nice balance.

Now the particles look like a painted light streak effect. In the Particle group, let's make a few cosmetic changes. Change the Color to red, the Size to 12, Transfer Mode to Add, and Opacity to 40. You've just created an iPod effect!