Unity Gaming: Polish – Particles!

So far in this series I’ve showed you how to make an infinite runner; talking about spawners, destoryers, character controls, handling collisions, and music. Now I’ll show you another way to polish your game; Particle Effects. Particle Effects are an easy way to add that extra wow factor to your game without too much effort.

There are several things you can do with the Particle System Unity provides. You can make streams of water, fire works, explosions, lightning bolts, OR ominous yellow radioactive acid fog (the 100 reference, you should watch it, it’s on Netflix) I find the best way to learn about how to create all the different effects is to play with them yourself. So, by the end of this post you will have a barrel leaking yellow radioactive material shown below.

Unity_Radioactive_Barrel

I’ll also talk about WHY the particles look like they do and HOW we can effect them through the editor.

Understanding Particle Systems

Particle Effects are generated by a Particle System. Any gameobject within Unity can have a Particle System component.

A Particle System is, at it’s core, a Spawner, that spawns texture sheets at a specific location with certain properties defining lifetime and behavior. So we’ve done something like this before. However this time Unity provides a nice Inspector Menu to tweak the behavior and lifetime of the object being spawned. Also, Unity’s Particle System is dynamic. This allows the emission and lifetime settings affect the overall behavior of the system but the individual particles can also change over time.

Unity also provides lots of documentation on each module of the Particle System. Modules are the different sections in the Particle System Component in Unity. Now, I won’t go over all the modules of a Particle System and their properties but I’ll definitely highlight the popular ones as we make the prefab.

  1. Main, Emission
  2. Shape
  3. Color Over Time
  4. Size over lifetime
  5. Collision
  6. Sub Emitters
  7. Renderer

Step 1: Set Up and Default Emitter

So in a new scene I’ve added a Cylinder and a plane to the scene along with an empty GameObject and called it Particles. I then rotated the Particles object -90 in the X axis of the transform and added a particle system component to it.

1-0-Particles

Once you’ve added the particle system to your scene you will see little white glowing balls of light being generated and then disappearing. This is because of Unity’s default settings for it’s Particle system.

1-1-ParticleGenerated

1-2-ParticlesInspector

The little balls of light are created because that’s the current texture assigned to the system. The texture could be changed to whatever you want, like pictures of your face or smoke. I’ll talk more about textures and shaders later on. The point at which the particles are generated is called the Emitter.

Step 2: Main

The Main module of the Particle System controls properties of the system overall.

2-0-Main

Duration is the length of time the system will run. Most of the properties in this module control the initial behavior of the particles from the emitter. I’ve made the duration 5.00 which translates to 5 seconds.

Looping – This boolean value triggers whether or not the system will loop. If selected it will then repeat in 5 second (the duration) intervals.

**SIDE NOTE: Start Delay, Lifetime, Speed, and Size can be customized by selecting the down arrow on the side, and selecting one of the following options: Constant, Curve, Random between Two Curves, and Random Between Two Constants (The 4 Options). These Options allow the System to behave dynamically, emitting particles at different sizes, at different times, and with different speeds.

Start Delay: 0 – How many seconds after the system start would you like the first particles to be emitted.
Start Lifetime: 5 – Lifetime for the the individual particles emitted
Start Speed: 2 – How fast the particle travels outward from the emitter
Start Size: 4, 7 (Random between two constants)- How large the particles will be

Start Color – Yellow and Light green. I also selected Random Between Two Colors. You can choose whatever colors you want.

Gravity Modifier – 0.1 – Scales the gravity value set in the physics manager. A value of zero will switch gravity off. With the Gravity Modifier you do not need to use a lot of force. Play around and see what little gravity you need to force your particles straight down after emission… Hint, it won’t be a lot.

Main should eventually look like this now.

3-1-Main

Step 3: Emission

Rate – 3, 5 – Random Between Two Constants. Unity explains that the rate of emission can be constant or can vary over the lifetime of the system according to a curve. If Distance mode is selected then a certain number of particles are released per unit of distance moved by the parent object. This is very useful for simulating particles that are actually created by the motion of the object (eg, dust from a car’s wheels on a dirt track). However, Distance mode is only available when Simulation Space is set to World in the Particle System section.

3-1-Emission

Step 4: Shape

The Emitter can multiple shapes

    • Sphere
    • Hemisphere
    • Cone
    • Box
    • Mesh
    • Mesh Renderer
    • Skinned Mesh Renderer
    • Circle
    • Edge

3-1-Shape

I’ve selected Cone since I want the particles to fountain out of the Barrel.
Angle – 30
Radius – 1 – Same as the radius of the barrel.
Emit from: Base

Step 5: Color Over Lifetime

Color Over Lifetime can be set with one Gradient or Random Between Two Gradients. I’ve chosen Gradient, and set the color to White; and then changing the alphas at the beginning and end to 0 to fade in and then fade out creating a radiating glow from the particles. You can change the colors and alpha for the gradient by clicking on the gradient field.

3-3-ColorOverLifetime

Step 6: Size Over Lifetime

To Edit the curve of Size over Lifetime you need to open the editor for Particle Editing. At the top of the Particle System Component in the Inspector Click – Open Editor…

3-4-SizeOverTime

Once the Editor has popup you will see the settings for your particle system as well as a graph. Unity has some default curves for you to choose from at the bottom of the grid. My curve starts at .5 and arcs up to 1.

3-4-SizeOverTimeGrid

You can also use the editor to tweak the modules that we were editing before.

Step 7: Collision

The collision module determines whether or not the particles will collide with 3D, 2D, or plane objects. I have it selected because on collision I want a secondary effect to happen, which we can edit with the sub-emitter module.

3-5-Collision

I’ve chosen my particles to collide with objects in the 3D World space, with no dampening force or bounce on the particles so they stay on the ground and keep their velocity. I also want dynamic collisions but not with itself. I could also check the box for Send Collision Message, but I’ll save that for later.

Step 8: Sub Emitters

Sub Emitters are secondary particle systems that are parented to the initial particle system created. They are great for creating secondary effects on actions. Unity likes using the example of a bullet that might be accompanied by a puff of powder smoke as it leaves the gun barrel and a fireball that might explode on impact. Those sub-emitters would be added to the Birth and Collision section respectively. Since sub-emitters are simply particles systems they can have sub emitters of their own, allowing you to create complex effects like fireworks. However BE CAREFUL this can lead to a numerous amount of particles in your scene and slow performance greatly.

When you initially look at the Sub Emitter Module it contains three sections, Birth, Collision, Death with two slots each, saying, “None”.

4-0-SubEmitter

As I mentioned before I want my particles to have a secondary effect on their collision. So to add a sub-emitter to my scene I simply have to select the plus sign next to the first Collision slot. The default sub-emitter of white lights will be created. To prevent the onslaught of pretty white lights filling up my scene, get ready to click stop on the particle system in the scene tab. This will save you a lot of grief as your machine might slow down a bit.

4-1-Stop

Now to save time I’ll screen shot the modules of the sub-emitter for you to copy.

4-2-SubEmitter

PART 2.

4-3-SubEmitter

I’ve only changed a few things. The shape of the sub-emitter is a hemisphere, and the color over lifetime is a bit more colorful. Also notice that the Collision module is on as well but I do not have any more sub-emitters attached.

Step 9: Renderer

Now this module is related to the texture sheet that is attached to the particle system. Overall the Renderer determines how a particle’s image or mesh is transformed, shaded and overdrawn by other particles. Since we are using the default texture sheet I’ve kept the Renderer settings on their default as well.

5-1-Renderer

Tweaking the System

Now there are several other examples that you can checkout from Unity in the editor. Simply go to Assets and Import the Particles Package

6-1-ImportParticleSystem

And there you have it! Your first Particle System! Now take what you’ve learned and play around with more of the settings. I did skip over some things, like Send Collision Messages, and the Texture Sheet Animation module. I will cover those in my next post where we have these systems interact with our player.

Happy Coding!

-TheNappingKat


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