The room is built. The sky is settled. And it still looks somehow frozen.
That's because nothing is moving. A flickering light, rising motes, drifting dust. One small motion makes a space look alive.
This article builds one column of rising motes of light. Along the way, we'll look at what actually makes particles expensive.
What You'll Learn
- The five settings to touch first
- The shortest path to glowing motes
- That covered area, not particle count, drives cost
- Two small tricks that improve the look
Start from having read materials and textures.
Only five things to touch
Add a Particle System and twenty-plus foldouts appear in the Inspector. You don't need to understand all of them.
Five are what you touch first.
| Setting | What it decides | Where it lives |
|---|---|---|
| Looping | Repeat, or finish after one pass | Main |
| Start Lifetime | Seconds before one particle disappears | Main |
| Start Speed | Speed at emission | Main |
| Start Size | The size of one particle | Main |
| Rate over Time | How many emit per second | Emission |
Those five shape most effects.
Putting the judgment into words too:
- Things you want emitting continuously (steam, dust, motes of light) get Looping on
- One-shot things (explosions, a flash on pickup) get Looping off
- Start Lifetime and Start Speed decide how high it reaches. Speed × seconds is roughly the travel distance
- Start Rate over Time small. Jumping straight to 100 makes it impossible to see one particle
Hands-On: Build rising motes of light
Build an effect where motes of light rise quietly from one corner of the floor.
1. Prepare the look of one particle
First, decide what one particle looks like.
Right-click in the Project window, choose "Create → Material," and name it GlowParticle. In the Shader field, pick Particles → Standard Unlit.
| Field | Setting |
|---|---|
| Rendering Mode | Additive (overlaps get brighter) |
| Color | Pale blue or white |
| Albedo (texture) | A small circle image, bright at the center and fading at the edges |
If you don't have a circle image on hand, no texture is fine. The particles come out square, but that stops mattering once they're small.
Additive is chosen because we want it to read as light. Overlapping areas get brighter, giving the sense of a glow.
2. Place the Particle System
Right-click in the Hierarchy, choose "Effects → Particle System," and name it GlowMotes. Put it around (0, 0.1, 3), just above the floor.
From the moment you add it, white particles should be blasting out. We change the five settings from here.
In the Main foldout, set this.
| Field | Value |
|---|---|
| Duration | 5 |
| Looping | On |
| Start Lifetime | 4 |
| Start Speed | 0.3 |
| Start Size | 0.08 |
| Max Particles | 100 |
In the Emission foldout, set Rate over Time to 8.
In the Renderer foldout, drag GlowParticle into Material.
At this point you should have small lights rising slowly.
3. Decide the emission shape
Open the Shape foldout. This is where the emission area and direction are set.
| Shape | How it emits | What it suits |
|---|---|---|
| Cone | Spreads in a cone | Fountains, flames, jets of steam |
| Box | Evenly from inside a box | Dust drifting in a room, snow |
| Sphere | Outward in all directions | Explosions, a flash on pickup |
Since this is light rising from the floor, set it like this.
| Field | Value |
|---|---|
| Shape | Box |
| Scale | (2, 0.1, 2) |
Particles now spawn evenly from inside a thin slab. That reads more naturally than jetting from a single point.
4. Build the fade-out
As it stands, particles vanish abruptly at the moment their lifetime ends. Fixing this makes it look far more convincing.
Enable the Color over Lifetime foldout. Clicking the color field opens a gradient editor.
Set the opacity handles along the top like this.
| Position | Opacity |
|---|---|
| 0% (at birth) | 0 |
| 20% | 255 |
| 100% (at death) | 0 |
Now they fade in and fade out.
Enabling Size over Lifetime as well changes size across the lifetime. Picking a curve that shrinks makes the fade-out even more natural.
These two alone change the look dramatically. You can leave the other modules alone for a good while.
5. See the cost with your own eyes
Here's the article's other purpose.
While in Play, open "Stats" in the Game view. Note the current numbers.
Then try these two separately.
| What to try | Value to change | Look | Cost |
|---|---|---|---|
| A: Ten times the particles | Rate over Time to 80 | Denser | Barely changes |
| B: Ten times the size | Start Size to 0.8 | The screen fills with light | Clearly heavier |
B is heavier. Raising size hits harder than raising count.
The next section explains why. Once you've confirmed it, put them back to 0.08 and 8.
Cost comes from area, not count
Translucent things are drawn on top of what's behind them, without erasing it.
Where three particles overlap, that area is painted three times. Ten overlapping means ten times. That repainting is called overdraw.
So this is how it lands.
| Situation | Cost |
|---|---|
| 100 small particles, spread out | Light |
| 10 large particles, overlapping across the screen | Heavy |
What matters isn't "how many particles" but "how much of the screen, painted how many times."
The steps to make it lighter follow from that.
- Make particles smaller (biggest effect)
- Don't put them too close to the camera. Avoid arrangements that spread large right in front of your eyes
- Cut the count
- Disable the whole object for particles nobody can see
Put the other way, plenty of small particles is fine. Emitting 100 scattered motes of light is usually no problem at all.
If you're also building for Quest, this matters especially. Large translucent surfaces covering the screen are the first candidates to cut.
Common Pitfalls
- No particles visible → Start Size is too small, or no material is assigned
- The particles are square → There's no texture. Add a circle image, or shrink them until it doesn't show
- They scatter violently → Start Speed is too high. Try around
0.3 - They vanish abruptly and look wrong → Build a fade-out with Color over Lifetime
- It's heavy → Lower Start Size. Look at size before count
- Jetting from a point looks unnatural → Set Shape to
Boxand widen the area
Bonus: Good to Know Up Front
- Particles aren't synchronized: They play separately on each screen. Fine for effects, but if you want "the firework went up now" to land for everyone at once, send the cue with network events
- Turning off Play On Awake lets you fire it on press: Calling
Play()from Udon lets a button trigger the effect. Useful for a flash on pickup, a celebration at the goal - One addition to a still room goes a long way: A flickering light, drifting dust, steam. One moving thing changes the impression of the space
- Max Particles is insurance: It caps how many appear when you get a setting wrong. Keeping it low prevents accidents
- It's useful all over: Campfire sparks, underwater bubbles, magic effects, snow and rain, confetti at the goal. All of them start from the same five settings
Summary
Particles take shape from five settings.
- Looping, Start Lifetime, Start Speed, Start Size, Rate over Time
- Emission shape comes from Shape. A flat Box for emitting from the floor
- Building a fade-out with Color over Lifetime makes it convincing in one step
- Cost comes from screen area covered, not particle count
The question to ask before placing one is: "How much of the screen will this cover?" If it's small, you barely need to worry about the count.
To set mood with sky and fog, go to sky and fog set the mood. To make rendering lighter, go to making rendering lighter.