The shortest Fusion particle setup that actually shows you something is pEmitter → pRender → Merge → MediaOut. pEmitter creates and updates the particle set, but it never hands you a picture you can composite. pRender is the node that turns that particle data into an image. Switch pRender to 2D output, plug it into the green foreground input of a Merge, put your footage on the orange background input, and send the Merge to MediaOut. That is the whole skeleton.
Start with a plain dot field before you go after smoke, sparks or magic trails. A particle system gets far easier to diagnose when you change one group of controls at a time: emission, lifespan, initial motion, forces, appearance, and only then compositing. If the node graph still feels foreign, read the Fusion beginner guide first. I'm assuming here that you already know connections decide the image flow, not where a node happens to sit on the canvas.
Build the First Particle Node Chain
- Select a timeline clip and open the Fusion page. Confirm the existing MediaIn-to-MediaOut route before adding anything.
- Press Shift+Spacebar, search for pEmitter, and add it to an empty part of the flow.
- Add pRender and connect pEmitter to its particle input. Load pRender into a viewer with the 1 or 2 key. If the branch still shows nothing, move the playhead later in the comp so particles have had time to be born. After a jump of more than one frame, click Pre-Roll in pRender so particle positions are recalculated from the start of the render range.
- pRender defaults to 3D output, so click the 2D button under Output Mode when the goal is an ordinary overlay. A 3D particle output belongs in a 3D scene and won't behave like a flat foreground plugged straight into a standard Merge.
- Add a Merge. Connect MediaIn to the orange background input, pRender to the green foreground input, and the Merge output to MediaOut.
This split between the first two nodes is where most beginners get stuck. The pEmitter reference says it plainly: pEmitter outputs particle data, not a visible image, so a viewer has nothing to show. The pRender reference places the renderer at the end of the branch, where it converts that set into something the rest of the comp can use. So if you select pEmitter, press 1 and get an empty viewer, nothing is broken. View pRender or the final Merge instead.
Shape Where Particles Are Born
Select pEmitter and start in its Region tab. A new pEmitter uses a Sphere region; shrink its Size and you get the tight source that suits sparks or a fountain. Line, Rectangle, Bézier and Bitmap regions spread the birth positions across a bigger area. Let the shot decide: falling snow wants a wide source above the frame, while a welding spark wants a tight one right at the contact point.
Keep the region in plain view while you build. Park it well inside the frame and use a moderate particle count. A source outside the frame can be exactly right for rain or drifting dust, but during setup it only adds a mystery you don't need. Push it past the edge once the system is visible and predictable.
The Style menu decides how each particle is drawn. I'd start with Point, which draws single-pixel particles, or Blob for soft round ones, so speed and lifetime stay obvious. Move to Bitmap or a fancier style after the motion works, because an ornate style hides a bad emission path behind glow, blur and texture. If you do go Bitmap, the manual's advice is to keep that image small and square, around 256 × 256 pixels, since it gets duplicated into potentially thousands of particles.
Control Count, Lifespan, Velocity and Spread
Four pEmitter controls do most of the early work:
- Number sets how many new particles are born on each frame. A value of 1 adds one particle per frame, so by frame 10 you have ten. Treat it as density, not brightness. More particles cost more to calculate and can turn clean motion into a solid mass.
- Lifespan sets how long each particle lives, and the default is 100 frames. Too short, and particles die close to the emitter; too long, and they pile up through the shot and give pRender more to process. Lifespan Variance lets individual particles live a little longer or shorter so they don't all vanish on the same frame.
- Velocity gives particles their starting speed. Raise it when they need to clear the source quickly; lower it for dust, fog-like drift or a field that seems to hang in the air.
- Angle and spread controls (Angle and Angle Variance in the Inspector) set the starting direction and how far individual paths stray from it. A narrow cone reads as a jet. A wide cone reads as a spray.
Adjust them in that order. First make enough particles to read the shape. Then give each one enough life to travel through the part of the frame you care about. Only then tune speed and spread. Crank all four at once and a blank frame turns into a slow, overfilled comp that tells you nothing about which setting did it.
Particle values depend on the comp's timing and dimensions, so a setting lifted from another tutorial is a starting point at best. A fast 24-frame burst and a slow ten-second snowfall need very different relationships between Number, Lifespan and Velocity. Watch the full path from birth to disappearance; one copied number means little on its own.
Add Natural Motion With pTurbulence
Perfectly straight trajectories look synthetic because every particle gets the same kind of motion. Put pTurbulence between pEmitter and pRender:
pEmitter → pTurbulence → pRender
pTurbulence adds uneven, frequency-based variation across the particle field. Strength controls how hard the paths bend; the density and frequency-related controls change the scale and busyness of that variation. Small, slow changes suit drifting dust. Stronger, tighter variation can give you agitated sparks or magical energy, and it can just as easily give you random noise.
Treat the force as a correction on top of readable base motion, not as the only thing steering the particles. Set pEmitter velocity first so the system has a clear general path, then add turbulence until neighboring particles stop traveling as one rigid cloud. The pTurbulence node reference confirms that it belongs inside the particle branch, before pRender.
Create a Gravity-Like Fall With pDirectionalForce
For a uniform pull in one direction, Fusion's documented tool is pDirectionalForce. It goes between the emitter and the renderer, same as pTurbulence. Out of the box it already pulls down along Y at −90 degrees and affects every particle, which is why it behaves like gravity the moment you add it. Raise Strength to make sparks arc and fall or to speed up rain; turn the direction sideways for wind.
A useful branch can contain both forces:
pEmitter → pTurbulence → pDirectionalForce → pRender
Order can change the feel, because each node updates the particle set before passing it along. In a beginner comp, keep the graph readable and compare one order against the other instead of stacking duplicate forces. The pDirectionalForce reference explains that downward default: simulating gravity is this node's most common use.
Composite Particles Over Footage
Once pRender is putting out a 2D image with transparency, treat it like any other foreground. Send it to the green input of a Merge and keep the untouched footage on orange. The background branch stays clean and the layer order stays obvious.
If the particles need to sit behind a title but in front of the footage, use two Merge nodes: particles over footage first, then the title over that result. If the emitter has to follow a moving sign, hand, vehicle or anything else in the shot, solve that movement separately and apply it to the particle source or the rendered branch; a Line region's end points, for example, can be connected to Paths or Trackers. The Fusion tracking guide covers point and planar tracking. No particle force tracks scene movement for you.
Check alpha as well as RGB. Particles that look fine over black can show hard squares, dark fringes or weak edges over a bright shot. Keep the particle branch transparent and judge its appearance over the real background before you make final decisions.
Animate a Short Particle Burst
Continuous emission suits snow, dust or rain. Sparks, impacts and transitions usually want a burst. Animate pEmitter's Number so it sits at zero before the event, rises for a short stretch, then drops back to zero. The manual's own example works the same way: five particles per frame on frames 0–4, then a key of zero on frame 5, for 25 particles in total. Particles that were already born keep moving until their lifespan runs out; lowering Number only stops new births.
- Move to the frame just before the event. Set Number to zero and enable its keyframe.
- Move to the burst frame and raise Number enough to create the required density.
- Move a few frames later and return Number to zero.
- Play past the last emission keyframe. Adjust Lifespan if the tail ends too early or hangs around too long.
A narrow peak gives a sharp impact. A longer plateau gives a sustained spray. Reach for the Spline Editor only when the birth rate needs a shaped ramp; plain stepped or closely spaced keyframes are usually cleaner for a sudden burst. The keyframes and Curve Editor guide explains interpolation without tying it to one effect.
Why Nothing Appears
Check the graph in this order:
- You are viewing pEmitter. It only outputs particle data. Load pRender or the final Merge into a viewer.
- pRender is missing or disconnected. The particle branch has to pass through a renderer before it becomes an image, and for a normal Merge that renderer needs to be in 2D mode.
- The playhead is too early. Move later so particles have been born, especially when the emitter starts after the comp's first frame.
- Number is zero. Check the animated value at the current frame. A burst may already be over, or may not have started yet.
- Lifespan is too short. Particles can die before they ever reach the visible area.
- The region is outside frame and velocity points away. Move the source to the center for now and remove the forces until the field shows up.
- The wrong branch reaches MediaOut. Trace the final Merge output all the way to MediaOut.
Fix a Black Frame or Wrong Layer Order
If the particle result replaces your footage with black, look at the final composite rather than pRender on its own. A particle viewer shows transparent areas against the viewer's black background even when alpha is fine. Connect pRender to the Merge foreground and the footage to its background, then view the Merge.
If particles disappear behind the shot, the Merge inputs may be swapped, or a later Merge may be covering the result. Follow the branch from left to right and load each Merge into a viewer. In Fusion the green input is foreground and orange is background. A full-frame Background node placed over the particle result will also hide everything beneath it unless you mask it or reorder it.
Fix Rigid Motion and Early Disappearance
When the whole field moves like one object, widen the emitter's directional spread with Angle Variance and vary the initial motion, then add a restrained pTurbulence. A Transform node after pRender moves the already rendered particle image as a single layer. That's handy for repositioning the complete effect, but it adds no variation between particles.
When particles vanish too soon, raise Lifespan or reduce Velocity so they stay in frame longer. When they never seem to clear, shorten Lifespan or cut back the continuous emission. Watch the oldest particles, not just the newest ones near the source.
Keep Particle Comps Responsive
Particle systems get expensive because the renderer evaluates many changing elements across many frames. Keep Number low while you design the motion. Use a simple particle style, go easy on motion blur and glow, and preview at a reduced viewer resolution. Bring density and finishing effects up after the path is approved.
Long lifespan plus continuous emission is the classic performance trap: every frame can hold particles born across a long run of earlier frames. Trim Lifespan to what the shot needs. Each particle frame also depends on the one before it, so jumping more than one frame at a time can give an inaccurate image; Automatic Pre-Roll in pRender recalculates for you whenever the frame changes. If the effect should already be in motion when the edit starts, start the emitter earlier, or the first visible frame can look oddly empty.
For reusable work, expose only the controls the next editor needs, and only after the comp is stable. The Fusion macros and templates guide covers publishing controls and saving an Edit-page template. Don't package a half-diagnosed graph with twenty near-identical sliders.
Particles vs Stock Overlays and Ordinary Animation
Use Fusion particles when the effect has to react to the shot: the emitter needs a specific position, the motion needs forces, the density changes over time, or the result has to be rebuilt at different sizes and durations. That's where the procedural graph earns its complexity.
Use a stock overlay when speed matters more than customization and a suitable element already exists. A well-keyed spark or dust plate can be quicker to place and easier to preview. Check its resolution, frame rate, alpha or blend-mode requirements, and license before you rely on it.
Use ordinary keyframed graphics when you only need a handful of dots, stars or icons moving along known paths. Five controlled shapes don't need a simulation. Particle tools pay off when there are so many individual elements that animating them by hand stops being practical.
Particle Workflow Checklist
- View pRender or the final Merge, not pEmitter.
- Use pRender’s 2D output for a standard Merge over footage.
- Make the basic field visible before moving the emitter outside frame.
- Tune Number, Lifespan, Velocity and spread before adding forces.
- Insert pTurbulence or pDirectionalForce before pRender.
- Keep footage on the Merge background and particles on the foreground.
- For a burst, animate emission and let existing particles finish their lifespan.
- Reduce particle count and expensive finishing effects while designing motion.
- Inspect the complete composite on both dark and bright frames.
- Render a short proof around the hardest section before committing to a long delivery.
The finished graph should still be easy to read: one emitter, only the forces that shape the motion, one renderer, and a deliberate composite into MediaOut. That simple structure is enough for falling dust, sparks, snow, drifting particles and plenty of stylized transitions without losing track of where the image actually comes from.
