Particle System 2: Emission & Shape Module

Overview

Two of the most important modules in Unity’s Particle System are Emission and Shape. Together they answer: how many particles? and from where?

Emission Module

The Emission module controls the rate at which particles are spawned.

Rate over Time vs Rate over Distance

Setting	Use case
Rate over Time	Continuous effects like fire, smoke, waterfalls
Rate over Distance	Effects that respond to movement (tire tracks, dust from footsteps)

Bursts

Bursts let you emit a fixed number of particles at specific times. Perfect for:

• Explosions (single large burst)
• Muzzle flash (burst on trigger)
• Confetti cannons

Burst settings:

• Time — when in the particle system’s lifetime to fire
• Count — how many particles to emit
• Cycles — how many times to repeat
• Interval — time between repeated bursts
• Probability — chance (0–1) that the burst fires each cycle

Shape Module

The Shape module defines the 3D emitter geometry — where in space particles originate and in what initial direction they travel.

Common shapes

• Sphere — Particles emit from the surface or volume of a sphere, outward in all directions. Great for explosions.
• Cone — The default. Particles emit from a disc and spread outward in a cone. Great for smoke, fire.
• Box — Particles emit from inside a box. Great for rain, snow (use a wide flat box above the scene).
• Circle — 2D ring emitter. Good for portals, magic circles.
• Mesh — Emit from the surface of any mesh. Powerful for character effects.

Emit from options

For Sphere and Cone you can choose to emit from:

• Volume — Random point inside the shape
• Shell/Edge — Only from the outer surface

Practical exercise

Try building a simple campfire effect using just these two modules:

1. Set Shape to Cone, angle ~15°, radius ~0.1
2. Set Emission Rate over Time to 30
3. Set Start Speed to 1–2 (use random between two constants)
4. Set Start Lifetime to 1.5s

In the next lesson we’ll add velocity modules to make the smoke drift realistically.