Particles

The Preset popup stamps one of 60 factory systems onto the dials, grouped by family under header rows in the popup (fire, smoke, embers, dust, sparks, weather, magic, sci-fi, liquids, nature). A look can carry the emitter shape and volume, aim, speed, rate and lifetime, size, forces, the draw mode, the Render mode, the Over Life curves, a sprite and, for lit looks, the lighting material. What the stored looks never carry is placement or the shot: Emitter Position, Emitter Z, Seed, the depth-of-field pair, Motion Blur and the light setup stay as you set them. Touch any dial afterward and the popup flips to Custom.

Seed re-rolls every random draw the system makes: same dials, different particles. It’s the fix for the one clump that lands badly across your subject — step it until the field misses, instead of bending Spread or Particles/sec to hide the problem. The number that produced the field you approved is sitting in the panel where you can read it, revert to it, and hand it off with the project.

Render decides how the field leaves the effect. Over composites the particles over the layer’s own content. Add and Screen blend them in instead, which is the right answer whenever the particles are light — sparks, embers, motes — rather than matter. Particles Only outputs them on their own alpha: the pass you want when the particles need their own grade or their own blur, or when something in the comp has to sit between them and the plate.

Motion Blur is the real thing, computed from each particle’s own motion. Comp Settings honors the comp’s shutter, so the field blurs like every other moving layer and sits in the same shutter as the plate. Custom unlocks Shutter Angle (Custom) and Shutter Phase (Custom) for a per-effect shutter — worth reaching for when the particles should smear harder than the footage does. Blur Samples trades smoothness against render time, and the amount you need scales with how far a particle travels inside one shutter — the default carries a drifting field, fast systems want more. Off is correct for slow fields, where the blur costs render time and changes nothing.

Depth of field comes from camera distance, not from a filter. DOF Aperture is the strength — how hard an out-of-focus particle goes soft — and DOF Focus Distance is where sharpness lives. Both default to 0, so the field is pin-sharp until you ask otherwise, and they only do useful work together. This is what turns a deep emitter volume into actual depth rather than just size variation, and keyframing DOF Focus Distance racks focus through the swarm.

Where particles come from, how many there are, and how fast they leave.

Emitter Shape picks the source geometry and decides which of the dials below matter. Point fires everything from one spot at Emitter Position, pushed into depth by Emitter Z — clean, but it reads as an effect unless something downstream scatters it. Box and Sphere fill a volume around that spot using Emitter Size X, Emitter Size Y, and Emitter Size Z; that volume is most of what separates weather from a jet, and giving it real depth in Emitter Size Z is what makes a field feel like it surrounds the camera instead of hanging on a card. Grid lays particles out on a regular lattice instead — Grid X by Grid Y by Grid Z positions spanning the same size box — for dot matrices, scan patterns, and anything that should read as ordered rather than natural.

Layer earns its own paragraph: particles emit from another layer’s pixels. Set Emitter Layer to the source, Emit From to Luminance or Alpha depending on whether brightness or coverage defines the shape, and Emit Threshold to decide which pixels qualify — raising it keeps soft antialiased edges from spraying stray particles and confines emission to the solid interior. A text layer needs no preparation at all here: the glyphs emit their own particles, which is the whole logo-dissolve setup in three dials.

Aim and rate. Direction X, Direction Y, and Direction Z form the launch vector — the default Direction Y = -1 fires upward — and Spread opens a cone around it, from a collimated line at the bottom of the range to a wide fan at the top. Speed is the launch velocity and Speed Random scatters it per particle; Speed Random 30–50 is what keeps a spray from moving like one object. Zeroing all three direction dials gives aimless emission instead, which is a different tool from a wide cone and a common one: 26 of the presets ship with the vector at zero. Most spend it on unaimed ambience, such as Magic Motes and Ash Fall, but Detonate Sparks zeroes it too, which is how a blast goes everywhere at once.

Population is three dials and a multiplication. Particles/sec is the continuous rate, Life (sec) is how long each particle survives, and the on-screen count is roughly the two multiplied — which is why raising life is often the cheaper way to fill a frame than raising rate. Life Random staggers the deaths so the field doesn’t pulse. Burst Count (cumulative) is the other emission mode entirely: it’s a running total, so a Hold keyframe that steps it up emits the difference on that frame and nothing after — set Particles/sec = 0 and the effect becomes a one-shot. Particles per Hit is the third route, used only by the Burst target in the Audio Drive group: it is how many particles one full-strength hit emits, and it can’t be keyframed. Inherit Velocity decides how much of an animated Emitter Position’s own motion newborn particles carry away with them: 100 hands them all of it, which is a torch trailing sparks as it swings, and 0 leaves each particle where it was born while the emitter moves on.

Particle Type decides what a single particle actually draws, and it changes the read further than color ever will. Soft Sphere is the plain soft dot — snow, ash, dust, anything that’s matter rather than light. Glow Sphere wraps that dot in a halo, which reads as light rather than matter. Streak stretches each particle along its own velocity so speed becomes visible: Streak Length (sec) sets how much of a particle’s recent travel the streak covers, so Streak Length (sec) = 0.033 is a light smear on fast sparks while Streak Length (sec) = 0.09 draws the long parallel lines of a warp field. Heat is not a reason to reach for Glow Sphere: the spark looks Cinder Sparks and Detonate Sparks both run Streak, and their warmth comes from Color and from how fast they move. Billboard draws your own artwork instead — assign a layer to Sprite (Billboard) and every particle becomes a camera-facing copy of it.

Sprite Shape gives Billboard a built-in image, with no layer needed: Soft Puff, Hard Puff, Wisp, Spark Point, Four-Point Star, Six-Point Star, Halo Ring, Hex, Snow Flake, Teardrop, Taper Streak or Bokeh Disc. Picking one switches Particle Type to Billboard and Sprite Layout to Single Sprite, so the shape shows right away. A sprite from Sprite Preset or a Sprite (Billboard) layer takes priority over the shape, and None (use layer) turns it off.

The sprite block reads that layer. Sprite Preset is the sprite-source popup, and its list is built when the effect loads; the entry to know is Custom (Sprite Layer), which takes the image from the layer you assigned. Sprite Layout then decides how it’s read: Single Sprite uses the whole frame as one image, Sheet Grid treats it as a sprite sheet cut into Sheet Columns by Sheet Rows cells. Sheet Playback picks how those cells are used — Loop cycles them at Sheet Rate (fps), Play Once runs through and holds, Over Life maps the whole sheet across each particle’s lifetime (the mode for a sheet that is the animation: a puff blooming, a spark flaring), and Random Still assigns one cell per particle and leaves it there, the cheap way to get shape variety out of a single sheet. Sheet Frames is for a sheet that isn’t full: set it to the number of real frames (13 frames on a 4 by 4 grid, say) so no particle lands on an empty cell and vanishes. At 0 the whole grid is used. Sheet Random Phase de-syncs the start frame per particle so a thousand looping sprites don’t animate in lockstep.

Size, opacity, and color are the base values every particle is drawn from. Particle Size is the base size in pixels, before camera distance and the Over Life curves scale it; Size Random is the per-particle variance, and Size Random 40–70 is what keeps snow and ash from looking machine-made, while a lattice or a starfield wants it near zero. Opacity is the flat multiplier over the whole system, and its low end is a technique rather than a mistake: Opacity = 10 with very large soft particles is how Smoke Rise builds density out of overlap instead of out of any single puff. Fade Over Life is on by default and takes each particle out toward the end of its life; switch it off for fields that should simply hang, the way Starfield Hang does. Color is the base tint everything starts from.

The glow block builds the halo. Glow Amount is how much each particle throws and Glow Size is how far it reaches; Glow Amount 90–150 with Glow Size 25–45 is the zone glow looks such as Magic Motes, Firefly Meadow and Grid Bloom live in, all three running Particle Type at Glow Sphere. Glow Falloff shapes the profile across that reach; its default is 100, and Firefly Meadow raises it to Glow Falloff = 130. Treat it as the last thing you touch, after amount and size have placed the halo.

Rotation only matters when a particle has a recognizable orientation, which in practice means Billboard sprites. Rotation sets the base angle and Rotation Random scatters it, defaulting to Rotation Random = 180 so sprites arrive at every orientation instead of all facing the same way. Spin (deg/sec) turns them while they fly — Spin (deg/sec) 60–180 is lively without becoming a propeller — and Spin Random varies that rate per particle so the field doesn’t rotate as one object.

Everything that acts on a particle after it’s born. This is the block that decides whether a field reads as physics or as a screensaver.

Gravity is the only force on by default, and its sign is the whole point: positive pulls particles down, negative floats them up. Snow, ash, and spark showers want it positive — Fountain Jet runs Gravity = 900 so its throw arcs over hard — while anything hot rises: Ember Drift sits at Gravity = -60 and Smoke Rise a touch gentler still. Wind X, Wind Y, and Wind Z add a constant push per axis, and a steady sideways drift is what turns falling particles into weather; Snow Drift uses Wind X = 40 and Ash Fall blows the other way at Wind X = -60.

Air Resistance is off by default and drags particles toward a stop. It fixes two specific problems: fast particles that fly forever, and sprays whose members all arrive at once. Air Resistance 0.4–0.6 is a light atmosphere on falling debris; Air Resistance = 1.8 is what kills Detonate Sparks a few frames after the blast, which is the difference between sparks and confetti.

Turbulence is a coherent noise field pushing on every particle, and four dials shape it. Turbulence is the strength: under 100 it’s a nudge that keeps a field from looking rigid, Turbulence 200–600 is the organic-swirl zone, and past Turbulence = 1000 the field is driving the shot rather than the emitter. Turbulence Scale is the feature size of that field, and it matters more than the strength does — small values like Turbulence Scale = 60 jitter each particle independently, which reads as noise, while Turbulence Scale 200–400 moves whole clumps together, which reads as air. Turbulence Evolution is how fast the field itself changes: Turbulence Evolution = 0 freezes it into a fixed pattern particles fly through, and Turbulence Evolution 0.3–0.6 is the slow boil the drift presets use. Turbulence Detail stacks octaves of finer noise on top — 1 is smooth and cheap, 4 adds fine structure over the large motion. Leave it where it sits unless the swirl looks too clean or too busy.

Sphere Force is a spherical attractor/repulsor for the shots the other forces can’t reach. Sphere Center places it in the frame, Sphere Z sets its depth, and Sphere Radius its reach. The sign flips it between pulling particles toward the center and pushing them away from it, so one dial covers both the collapse-into-a-point shot and the shockwave clearing the frame. Keep its strength in proportion to the gravity and turbulence already running or it simply takes over: Sphere Force 200–600 bends paths, and higher values own them.

Master Amount is the one macro dial here, and it scales the particle system’s emission and brightness inside the resolve, with 100 neutral. It works differently from a macro that writes to the dials it rides: nothing in the panel moves when you drag it, and there’s no dial you can read to see where it landed — the scaling happens where the system is solved. That makes it the fade handle. Keyframe it to bring a field up over a shot or take it out at a cut, and every relationship you dialed in underneath — rate against lifetime, size against glow — comes along unchanged.

Because it multiplies what the rest of the panel produces, a fade keyframed here and a fade keyframed below compound. Pick one place for a given move.

There’s no separate scale or speed macro on this effect, and it doesn’t need one — Particle Size, Speed, Life (sec), and the force dials are already native units you can scale directly when a look moves to a larger comp.

Each particle’s story across its own lifetime: three curves (size, opacity, color), each with stops at birth, a movable midpoint and death, plus an optional fourth stop, and the system interpolates between them. Read it as three curves, and they carry more of a look than the base values do: two systems with identical emitters read completely differently depending on whether particles arrive big and shrink or arrive small and swell.

Size Birth, Size Mid, and Size Death scale Particle Size at each stop, in percent, 100 neutral. The shape you pick is the character. Size Birth = 0 rising to Size Mid = 100 and falling to Size Death = 0 is the pop-and-vanish of a spark or a mote — nothing appears or disappears abruptly. A low birth climbing to a high death (Size Birth = 40 up to Size Death = 180) is how smoke and steam expand as they cool and slow. Holding all three at 100 keeps a constant size, which is what snow, ash, and starfields want.

Opacity Birth, Opacity Mid, and Opacity Death do the same for visibility. Fade Over Life is the one-checkbox version of this idea; these three are the explicit version, for when the fade needs to land earlier, later, or at both ends. Opacity Death = 0 gives a clean exit; Opacity Birth = 0 fades particles in, which matters whenever the emitter sits inside the frame and you don’t want to watch particles appear out of nothing. A dip at Opacity Mid is the flicker of a firefly rather than a fade.

Color Birth, Color Mid, and Color Death give a particle a color story instead of a single tint. White is neutral at all three. Set birth near white, mid to orange, and death to a deep red and every particle cools as it flies — the read that sells hot metal, embers, and anything recently on fire. Keep the three stops close together for a subtle drift; spread them far apart and the field visibly changes hue as it ages, which is a graphic effect and should be used as one.

Moving the stops. Size Mid At, Opacity Mid At and Color Mid At move each curve’s middle stop along the life, in percent (50 is halfway), so a puff can reach full size early and hold, or a spark can stay hot until late. Size Late At, Opacity Late At and Color Late At switch on a fourth stop at that point in the life, with its own value in Size Late, Opacity Late and Color Late. At 0, the default, the fourth stop is off and the curve is the plain three-stop one. The extra stop is what a hold-then-fade needs: Opacity Birth = 0, Opacity Mid At = 15 with Opacity Mid = 100, Opacity Late At = 80 with Opacity Late = 100, and Opacity Death = 0 fades a particle in fast, holds it, and fades it out late. A late stop placed before the mid stop is fine; the stops sort themselves into order.

Presets set these curves as part of their look, so check them after a preset pick before you build your own.

Lighting shades the particles with light from the scene, so smoke gets a lit side and a shadow side and debris reads as solid chunks instead of flat dots. Light Source picks where the light comes from. Off, the default, leaves the particles unlit and renders exactly as without this group. Comp Lights uses the comp’s own light layers, up to eight, read from the top of the layer stack down, including their color, intensity, spot cone and falloff. Key Light uses a built-in light set in this group, so particles can be lit with no light layer at all. Comp + Key uses both. With Comp Lights in a comp that has no lights, the particles get only the Ambient level. Lights work in comp pixels, so a light’s position and falloff distances read straight off the comp. Lighting is applied at render time and never re-simulates the particles, so moving a light is cheap.

The material. These dials describe how the particles take light, and presets set them as part of a look. Ambient is the floor every particle gets whatever the light direction (20 by default). Diffuse is the gain on the lit side. Wrap softens the line between lit and shadow sides: 0 is a hard edge, 100 wraps light around the particle the way it wraps around smoke. Backlight adds the glow of light coming through particles from behind, the rim you see on dust or smoke against a light. Highlight adds a specular hot spot and Highlight Size sets how broad it is, with smaller values giving a tighter spot. Light Tint is how much the lights’ colors tint the particles; at 0 every light acts as white. Shading picks Flat, one light value per particle, or Dome, which shades each particle like a small lit sphere that darkens toward its edge, and is what makes chunks and puffs look round. Self Shadow lets the cloud shadow itself, so particles behind other particles, as seen from a light that casts shadows, go darker. It is 0 (off) by default.

The scene. These belong to your shot, and presets never touch them. Falloff Scale scales the falloff distances of every light at once. Key Color, Key Intensity, Key Direction X, Key Direction Y and Key Direction Z set the built-in light. The direction is the way the light travels, in comp axes (x right, y down, z away from the camera), so the default sends light down, to the right and into the scene, as if from the upper left and in front. Key Casts Shadows lets the key light cast those self-shadows through the cloud (Self Shadow has to be above 0), and Key Shadow Softness blurs them, in pixels. A comp light casts when its own Casts Shadows option is on, with its Shadow Darkness and Shadow Diffusion.

Presets with a lit material, such as Hull Debris, Sunlit Cumulus or Kiln Ash, show it only once Light Source is set, since the light itself is part of your scene rather than the look.

Audio Drive lets a sound layer play the particle system. Set Audio Layer to any layer in the comp that carries audio, choose what to listen to and what it moves, and the effect follows the track with no keyframes. The group sits collapsed at the bottom of the effect. With Audio Layer set to None, or Drive Amount at 0, it does nothing at all and the effect renders exactly as it would without it.

What it hears. Listen To picks the part of the sound that does the driving. Loudness follows the overall level. Hits reacts to transients such as drum hits and impacts, and a strong hit pulses harder than a soft one. Bass, Low Mids, Mids, Highs and Air each follow one frequency band (roughly 20 to 120 Hz, 120 to 500 Hz, 500 Hz to 2 kHz, 2 to 8 kHz and 8 to 20 kHz). The drive hears the layer’s audio where it sits in the timeline, following the layer’s start time and any time stretch, but it ignores time remapping, trims, Levels and audio effects on that layer. So turning a layer down in the mix does not weaken the drive.

Shaping the signal. For Loudness and the bands, the level becomes a signal between two marks. Audio Threshold is the floor in dB: anything quieter reads as nothing. Audio Range is how many dB above the floor it takes to reach full signal. The defaults (a floor of -40 dB and a range of 40 dB) spread the whole swing from -40 dB up to 0 dB. Raise the floor to ignore room noise or quiet passages, and narrow the range for a jumpier reaction. Audio Attack and Audio Release, in milliseconds, set how fast the signal rises and falls; the defaults (10 and 180) rise quickly and fall back more slowly.

For Hits, Hit Threshold sets how far a transient has to stand out from the surrounding audio to count, so higher values keep only the strongest hits. Hit Decay is how long each hit’s pulse takes to fade, in milliseconds. Audio Sync Offset slides the reaction against the picture, in milliseconds: positive values make the picture react later, negative values earlier.

How hard it pushes. Drives picks the target and Drive Amount sets the depth. At the default 100, the target swings from zero in silence to twice its dialed value at full signal, passing through the value you dialed halfway. Lower amounts narrow that swing around your value, higher amounts widen it, and negative amounts flip it, so the target drops as the sound gets louder (a ducking effect).

What it moves. Burst emits a cloud of particles on every detected hit. The count is Particles per Hit (a top-level dial, 60 by default) scaled by the hit’s strength and by Drive Amount, capped at 20,000 per hit. With Listen To on a band or Loudness instead of Hits, the hits still trigger the bursts, but each one is scaled by that band’s level at the moment of the hit. A negative amount emits nothing.

Birth Rate, Velocity and Size scale Particles/sec, Speed and Particle Size, but only at the moment each particle is born. A particle keeps the speed and size it was born with, so a loud bar launches fast, big particles that carry on after the music drops, and scrubbing never rewrites particles already in flight. Brightness is the live one: it rides Master Amount and pulses everything on screen with the sound.

The driver dials apply to the whole history of the system at their current value, the same way the emitter setup does. Set them, rather than keyframing them.

More than one driver. Add Driver opens another driver inside the group, up to four in all, so one track can drive several things at once. A second driver has its own Listen To 2, Drives 2 and Drive Amount 2, plus a collapsed Response 2 group with its own Audio Threshold 2, Audio Range 2, Audio Attack 2, Audio Release 2, Hit Threshold 2 and Hit Decay 2. Drivers 3 and 4 repeat the same set with their own number. Remove Driver takes the last driver away. Every driver shares the Audio Layer and the Audio Sync Offset. Two drivers on the same target multiply their effects, except Burst: bursts from several drivers add up. The number of open drivers is kept in a hidden Drivers setting that the two buttons change for you.

Each frame works out its drive from the audio around it, so scrubbing, rendering in order or rendering out of order all give the same result.