TECH TIPS
Particles of Incorporation
After Effects Filter Provides Playground of Possibilities
by Ben Bardens
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Creating particles is an art. There are graphic artists and visual effects artists who specialize in doing particles. Particles don’t have to be just small sparkles of light; they can be little logos, shards of glass, bubbles, droplets, text, fireworks, explosions––basically whatever the shot calls for. Adobe After Effects contains several filters for creating particle effects to incorporate into your project. There are also several third-party filters designed for creating particles.
Of the effects included with the After Effects Pro version, the most powerful particle filter is Particle Playground. It’s a great name for a filter and makes it sound fun to use. But without any reference, this filter is more frustration than fun. In this tutorial, I’ll introduce some of the fundamental things to know about Particle Playground to start getting results. This tutorial and some of the techniques included are fairly advanced. If you aren’t already familiar with the basic interface and basic techniques for animating layers in After Effects, you may wish to refer back to the previous articles in this series. (For an index of these articles visit: www.glendale. edu/~bbardens and click on MPEG AE Training).
Download the sample files for this tutorial at: www.barkanimation.com/ guild/20.zip
You will need After Effects Pro (any version later than 4) and Photoshop (any version) to complete this tutorial.
Tutorial
Start by examining the “particle-comp.psd” file in Photoshop. Check out how the layers are set up, the size of the “particle,” and the gradients that make up the “layer map” layers. Keep these things in mind as you complete the steps in After Effects so that you can then create your own particles and layer maps later on.
Creating Particles with the Layer Exploder
Launch After Effects and create a new project. Import the “particlecomp. psd” file as a composition, using layer sizes (see figure 2).
 Fig. 2: Import Photoshop file as composition using layer sizes. |
Double-click to open the composition from the project window.
Choose Composition -> Composition Settings. If necessary, adjust your duration to 10 seconds. Note: if your duration was shorter than 10 seconds to start with, you will need to extend the out points for all your layers to match the new, longer duration. To do this, first zoom all the way out on the timeline and reveal the added time (hit the minus key on the alpha-numeric side of your keyboard a few times). Then type the end key on your keyboard, followed by Command A (Mac) or Control A (PC) and then type Option (Mac) or Alt (PC). This will select all the layers and trim new outpoints to match the new timeline duration. Type Shift Command A (Mac) or Shift Control A (PC) to deselect all and then hit the home key to return to time = 0 before continuing.
Disable the video switches for both the “layer map” layers and “particle” layer.
Choose Layer -> New -> Solid.
Name the solid “particle playground 1,” click the “make comp size” button and make solid color black. Click OK.
Drag the particle playground 1 layer beneath the logo layer in your layer stack.
With the particle playground 1 layer selected, choose Effect -> Simulation -> Particle Playground.
When the effect controls window appears, reposition and re-size the window as necessary to see both the effect control and composition windows.
Hit Shift and Page Down keys several times to jump forward along the timeline in 10-frame increments. You’ll see the default cannon particle generator shooting red pixels from the center of frame. Hit the Home key to return to time = 0.
In the effect control window, expand the Cannon subgroup and drag the Particles per Second value to 0. This turns off the Cannon particle generator.
Collapse the Cannon subgroup and expand the Layer Exploder subgroup. Make sure you are still at time = 0 and click the stopwatch for Radius of New Particles, leaving the value at 2.
From the pop-up next to Explode Layer, choose the “Logo layer.”
Push the page down key to step forward 1 frame. Change the value for Radius of New Particles to 0. Animating the Radius of New Particles property for the Layer Exploder allows you to control when the particles are created.
View a RAM preview (type 0 on the numeric keypad) and you’ll see that a group of particles are created in the shape of the logo at time = 0, and then rapidly fall toward the floor.
Change the Velocity Dispersion value to 20 (without setting a keyframe). Build another RAM preview. Notice that although the particles still fall rapidly toward the floor, they now scatter and drift slightly away from their starting position as they do so.
Collapse the Layer Exploder subgroup and expand the Gravity subgroup.
Change the Force value to 0 and then RAM preview the result. The particles now fly outward from the logo rather than toward the bottom of the screen.
We’ll now assign a custom particle image to each particle rather than the default pixels. Collapse the Gravity subgroup and expand the Layer Map subgroup.
Click on the pop-up menu next to Use Layer and choose the “particle” layer.
Preview your animation. To control the number of individual particles that appear, return to time = 0 and expand the Layer Exploder subgroup. Experiment with different values between 1 and 10 for the Radius of New Particles property (make sure you are at time = 0 each time you make the change so as not to create additional keyframes or change the timing). Notice that entering larger numbers results in fewer particles. This is because the value you input here gives you 1 particle for every n pixels of your Explode Layer image.
Collapse all open subgroups in the Particle Playground 1 effect control and save your project if you haven’t already.
To confine the particles to just the area of the frame around the logo, and to control the scale and opacity of our particles, we will now apply one of the layer maps that are included in the Photoshop file.
Expand the Persistent Property Mapper subgroup.
From the Use Layer as Map pop-up, choose “layer map 1.”
From the Map Red pop-up, choose “Scale.”
From the Map Green pop-up, choose “Opacity.”
From the Map Blue pop-up, choose “Lifespan.” To adjust the lifespan of the particles, change the Min value to 18 and the Max value to 28; this will keep the particles on screen longer.
Preview your animation and save your work. It looks good but could benefit from adding a few more particles. To create more particles, we need to add more keyframes for the Radius of New Particles property under the Layer Exploder subgroup.
Select your Particle Playground 1 layer in the timeline and push the U key on your keyboard to reveal the animating properties.
Click on the words “Radius of New Particles” to select all the keyframes for this property.
Choose Edit -> Copy.
Change the current time to time = 2 seconds and choose Edit -> Paste.
At this point, if you try and preview you’ll notice that it starts to take a very long time to build the preview. This is because between 00:01 and 02:00, the value for the property is in-betweening from 0 back to 2. So for every frame of that in-between, new particles are being created. The result is that very quickly you have literally thousands of particles in the animation and previewing grinds to a halt.
To bring things back under control and limit the particle creation so there are only particles being created at time = 0 and at time = 2 seconds (but not on every frame in-between), do this: In the timeline, click on the words “Radius of New Particles” again to select all the keyframes for this property.
Choose Animation -> Toggle Hold Keyframe. This removes all inbetweening from your keyframes so that each value holds right up until the next keyframe value.
Preview and save. Looks good. We’ll now add another different type of particle effect in the next series of steps.
Creating Particles with the Cannon
Make sure you are back at time = 0 and choose Layer -> New -> Solid.
In the solid settings dialog box, type in “Particle Playground 2” for the name, click the make comp size button and make sure the color is black. Click OK.
Leave the layer at the top of the stack and with it selected, choose Effect -> Particle Playground. (Particle Playground should be the second item in your effect menu because it was the last effect used. If not, apply it by choosing Effect -> Simulation -> Particle Playground.)
Expand the Cannon subgroup and resize the Effect Control window as necessary.
Push shift and page down several times to jump forward to about 2 seconds, so that you can see the default fountain of red particles created by the Cannon generator.
Change the Velocity value to 10. Notice that the particles now fall directly toward the ground rather than shooting upwards for a ways before being pulled down by the gravity.
Expand the Gravity subgroup and change the Force value to 10.
Preview your work. Notice how the particles now linger around the center of the frame (the location of the Cannon’s “barrel”) and then gently drift toward the bottom of frame pulled by the lower gravity force value. While there are other factors that can control particle movement as well, balancing the Velocity and Force values has a direct effect on particle behavior.
Collapse the Gravity subgroup and expand the Layer Map subgroup.
From the Use Layer pop-up, choose the “particle” layer to replace the default red pixels with our own custom particle from the Photoshop file.
Collapse the Layer Map subgroup and go back to the Cannon subgroup (expand if necessary). We will now animate the Position property to control where the Cannon is located during our animation.
 Fig. 3: The adjustment layer switch and expression "pick-whip" button in the Timeline window. |
Because animating the position value for many effect filters can be difficult to control and refine, we’ll copy and paste a path shape from Photoshop, apply to an adjustment layer and then use an expression to tie the Cannon’s position to it. You’ll need to launch Photoshop for the next step.
Open the “particle-comp.psd” file in Photoshop.
Locate the Paths palette (probably grouped together with the Layers and Channels palette, or choose Window -> Paths to locate). Notice there is a saved path in the palette called “motion path.” Single-click on the path to highlight it. Notice the shape of the path in the document window. This path was created ahead of time using the pen tool.
In the toolbox, locate the Path Selection Tool (or type A on your keyboard).
Using this tool, click and drag a marquee around the path in the document window to select all the points on the path.
Make sure all the points on the path are visible and choose Edit -> Copy.
Close the particle-comp.psd without saving and switch back to After Effects.
Push the Home key on your keyboard to return to time = 0.
Choose Layer -> New -> Solid.
In the solid settings dialogue, type in “motion path layer,” change the size to 10 pixels by 10 pixels, leave the color at black and click OK.
In the timeline, click the Adjustment Layer switch for the motion path layer you just created (see figure 3).
With the motion path layer selected, push the P key to reveal the position property.
Click on the word position to select it and then choose Edit -> Paste.
Notice the path we copied from Photoshop appears as a motion path for our new adjustment layer. Notice also that keyframes appear in the timeline. The keyframes in the middle, by default, are “roving” keyframes. This means that if we drag right or left on the last keyframe to adjust the speed for the motion path, the keyframes in the middle will adjust their location dynamically. Click on the last keyframe and drag it to time = 3 seconds.
Select the Particle Playground 2 layer and push the E key on your keyboard to reveal the effects.
Click the triangle to the left of the Particle Playground effect to reveal all its subgroups.
Click the triangle to the left of the Cannon subgroup to reveal its properties.
To add the expression, Option click (Mac) or Alt click (PC) on the stopwatch to the left of the Position property under the Cannon subgroup.
Then click and drag from the expression’s “pick whip” button to the Position property under your “motion path layer” (see figure 3). Make sure you click and drag from the pick whip button directly to the word “position” under the motion path layer and then release the mouse. This creates an expression linking these two properties.
Save and preview your work. Notice that the Cannon now follows the motion path. But there is one problem; when it reaches the end of the motion path, it simply sits at the end location and continues to emit particles. To solve the problem, we will keep our motion path moving by looping it and then animate the Particles per Second value to control the loops.
In the timeline, Option click (Mac) or Alt click (PC) on the stopwatch icon to the left of the Position property under our motion path layer to add an expression.
In the expression entry field to the right (where you see the highlighted word “Position”), replace it with this string: loopOut (type = “cycle”)
Make sure you enter the expression exactly as it is shown above and then push the Enter key on the numeric side of your keyboard (or click elsewhere in the grey workspace).
Preview your work. Notice that the stream of particles now loops over and over.
To fine-tune and finish the animation, apply these last few steps:
In the Particle Playground 2 Effect Controls window, expand the Cannon subgroup and change the Particles per Second value to 40 (without setting a keyframe).
Expand the Persistent Property Mapper. Choose “layer map 2” from the Use Layer as Map pop-up.
For the Map Red, Green and Blue pop-ups specify Opacity, Scale and Lifespan, respectively. Under Lifespan, change the Max value to 5.
To add a pause in between loops, add some keyframes to turn the Particles per Second value under the Cannon subgroup off and on. Add a keyframe at time = 0 with a value of 40, a keyframe at time = 3 seconds with a value of 0, a keyframe at time = 6 seconds with a value of 40 and a keyframe at time = 9 seconds with a value of 0. Select all four keyframes and then choose Animation -> Toggle Hold Keyframe.
Experiment with some of the settings in the other subgroups that we didn’t coSver. Also see what happens if you select the “particle/particlecomp. psd” footage item in the project window and replace it with something else by choosing File -> Replace Footage. Try replacing it with a little QuickTime movie of an animated particle or logo for example. Particle Playground is a deep and very powerful filter. For additional learning, choose Help -> After Effects Help. Then click on Search and type in “Particle Playground.”
Guild member Ben Bardens runs a graphics studio and works as an editor/technical director in the Burbank area. He teaches After Effects and Photoshop at Glendale Community College and can be reached at bbardens@glendale.edu. Find out more about his classes at www.glendale.edu/~bbardens.
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