Control Particles: Velocity, Color and Size Over Life in Niagara

From 'particles exist' to 'particles behave'

In the earlier lessons you spawned particles and toured the Niagara editor — the tool where you build particle effects in Unreal. Right now your particles probably just sit there, or drift in one boring lump. This lesson is where you take the wheel.

Every particle has a short life. The trick to good effects is deciding what happens during that life: how long it lasts, what color and size it starts at, which way it flies, what forces tug on it, and how it changes as it ages. Sparks shoot out fast and fade. Smoke rises slowly and swells. Embers fall under gravity and dim. You get all of that from a handful of modules and two little graphs called curves.

We'll work inside a single emitter. A 'module' is just one stackable behaviour you drop onto a particle (like 'add velocity'); an 'emitter' is the recipe that holds those modules. Don't worry if that's fuzzy — you'll see it click as we go.

Spawn vs Update — the one idea that explains everything

Niagara splits a particle's life into two groups of modules, and knowing which is which saves you hours of confusion.

Particle Spawn runs ONCE, at the instant a particle is born. This is where 'starting' values live — Initialize Particle (lifetime, color, size) and Add Velocity (the initial push) belong here.

Particle Update runs EVERY FRAME for the particle's whole life. This is where ongoing behaviour lives — gravity, drag, and the 'over life' curve modules that fade and shrink particles as they age.

Rule of thumb: if it's a one-time starting value, it's a Spawn module. If it changes the particle continuously, it's an Update module.

Shape one particle's life, start to finish

Do these in order inside your emitter's stack. After each '+' you'll search a little menu — type the words in quotes to find the module fast. Watch the Preview update as you go.

1. ✓
   1Set lifetime, color and size in Initialize Particle

   In the emitter stack, find the 'Initialize Particle' module under Particle Spawn and click it to show its settings on the right.

   Set 'Lifetime' to a fixed value like 2 (seconds) so particles live long enough to watch. Set 'Color' to something bright. Set 'Sprite Size' (or 'Uniform Sprite Size') to a clearly visible value.

   These are the values each particle is BORN with — change them and the Preview updates immediately.

   TipMany fields have a small dropdown to pick 'Random Range' instead of a single number. Giving Lifetime a range like 1 to 2 instantly makes the effect look less robotic.

2. ✓
   2Give particles a push with Add Velocity

   Still under Particle Spawn, click the '+' on the Particle Spawn group and add 'Add Velocity' (sometimes shown as 'Add Velocity in Cone' or 'Add Velocity from Point').

   Set a velocity so particles actually move. A cone mode sprays them outward in a fan; a simple linear velocity sends them all one way. Increase the speed and watch them shoot.

   Velocity is measured in Unreal units per second — bigger numbers, faster particles.

   TipAdd Velocity in Cone is the friendliest starting point: one slider for spread angle, one for speed. Widen the angle for a spray, narrow it for a jet.

3. ✓
   3Pull them down with a Gravity Force

   Now move to the Particle Update group (it runs every frame). Click its '+' and add 'Gravity Force'.

   Leave it at the default and watch: particles now arc and fall instead of flying in straight lines. That arc is velocity (the push) being bent by gravity (the force) over time.

   You can change the gravity strength or direction in the module if you want a moon-like float or a sideways pull.

   TipSeeing a graceful arc is the proof that Spawn and Update are working together: the Spawn push sets the launch, the Update force shapes the flight.

4. ✓
   4Slow them down with a Drag force

   Add a 'Drag' module to the Particle Update group as well.

   Raise the Drag amount and the particles decelerate — fast at first, then easing to a near-stop, like throwing confetti into still air.

   Drag is what turns a hard, gamey spray into something that feels like it's moving through air.

   TipTiny drag values go a long way. Nudge it up gently — too much drag freezes everything in place almost instantly.

5. ✓
   5Fade them out with Scale Color over life

   In Particle Update, add 'Scale Color' (sometimes called 'Color' with a curve, or 'Scale Sprite Color'). This multiplies the particle's color over its lifetime using a curve.

   Find the Alpha (opacity) curve and drag its right-hand point down to 0. Now particles start fully visible and fade to nothing as they die — no hard pop-out.

   The curve's horizontal axis is the particle's age from 0 (born) to 1 (dead); the vertical axis is the multiplier.

   TipFading alpha from 1 to 0 over life is the single most common 'this looks pro now' change. Almost every soft effect does it.

6. ✓
   6Shrink (or grow) them with Scale Size over life

   Also in Particle Update, add 'Scale Sprite Size' (a size-over-life module driven by a curve).

   To make sparks shrink as they fade, draw the curve from 1 at the left down to 0 at the right. To make smoke billow, do the opposite — start small and grow.

   Combine shrinking size with fading alpha and a single boring dot becomes a believable, dying ember.

   TipSize and color curves read the SAME 0-to-1 age axis, so a particle that's half-faded is also half-shrunk. They stay in sync for free.