When I first started out making games I thought
that these were what we called animations I associated particle effects with a more
continuous, looping, kind of visual effect not something that had a clear start and stop. But it turns out that these effects are actually
made using Unity’s particle system, and it confused me for a long time about how to
do that So in this video I’m going to give a very
clear explanation of how the particle system works in Unity, what the modifiers actually
do, and how these kinds of VFX are made. So to create a particle system you simply
right click in the hierarchy, go to effects and click particle system. We then get the default particle system and
a control panel in the bottom right Just click stop and ignore this for now What we want to look at is the inspector window. This shows us the particle system component
and this controls everything about how the particle system works. There’s a lot of scary modifiers so I’ll
start with the most important ones: duration, start lifetime, start delay and start speed. Duration is how long the particle system emits
for. But crucially, this doesn’t control how
long the effect will last, that’s very important to keep in mind. This only controls how long particles are
being emitted out of the system, so if you set it to 1, it will emit particles for 1
second then stop the emission. If we untick looping, which stops the effect
from repeating forever, and click play on the particle system you’ll see that the
system stops after some time, but note that if I stop the system after 1 second, there
are particles still active. You might expect the effect to only last 1
second but instead it goes on for 6 seconds before ending. That is because of the second modifier: start
lifetime. Start lifetime determines how long each particle
exists for after being emitted. This essentially acts like a countdown timer
that begins as soon as a particle is emitted. If you have multiple particles then each particle
emitted will last for this value and then disappear. This modifier contributes to the TOTAL length
of the effect. If duration is set to 1 and start lifetime
is set to 1, the total duration of the effect will never be more than 2 This is because a particle emitted at the
end of the duration, e.g at 0.99 seconds, will then exist for the start lifetime value
of 1 and so the final particle will be around until 1.99s from the first emission, or when
the system started. With this new value of 1 for start lifetime,
if I restart the particle system you will see that particles are emitted for up to 1
second, and after roughly 2 seconds the effect is finished. So remember, to control the length of a particle
effect you must use both duration and start lifetime. The next modifier on our list is start speed,
and this is only used for particles that need to move outwards or inwards. Right now our start speed is set to 5, notice
the speed at which the particles move outwards at this value. Now if I set this to 1, the particles travel
a lot slower. Two interesting things to note about this
modifier is that for particles you don’t want moving, this must be set to 0. Then restarting the system you can see the
particles are created, stay still, and then die, a bit like you. The other point to note is that if you want
particles to move inwards instead of outwards, set the speed to a negative value. If I set the speed to -2, you will see that
the particles move inwards and create a sort of coalescing effect. The final modifier is start delay. This is the delay before the system starts
to emit any particles When you’re creating an animation, or VFX
that doesn’t loop, any part of that effect that doesn’t start at the beginning must
have a non-zero value. If I set the start delay to 1, you will see
the particle system will wait for 1 second before starting. Notice that this affects the total length
of the particle system, with a start delay of 0, our effect lasted about 2 seconds. Now with a start delay of 1 it lasts 3 seconds. And that’s that. In my opinion, these 4 modifiers: duration,
start lifetime, start delay and start speed are the most important ones to completely
understand if you want to create VFX using Unity’s particle system. I’m now going to quickly go through the
examples I showed at the start, and show you how these 4 modifiers are driving the overall
effect. But before I do that I need to talk about
one other aspect of the particle system, and that’s the emission modifier. The panel below the one we’ve been working
on is called emission and this controls how the particle system emits particles. Rate over time controls how many particles
are emitted per second, so this value means that 10 particles are emitted per second. If our duration value is 1, which means the
particle system emits for 1 second before stopping, then the system should emit roughly
10 particles. I say roughly because there’s a slight delay
at the start before the first particle is emitted so it won’t be exactly 10 particles. Now I bring the Emission modifier up because
the visual effects I’m about to show you all act more like an animation, with a start
and a stop. To make these kinds of effects, we don’t
emit particles over time, but instead set the emission to a single burst. See how the particle system emits particles
one after another for one second currently. If I set the rate over time to 0, and press
play, no particles are emitted. But if I add burst emission by clicking the
plus sign in the bottom right, the particles will be emitted together in a single burst. The number of particles is controlled by the
value under count. Burst emissions are heavily used to create
the non-continuous effects seen in most video games, for example the VFX used for character
abilities, gun muzzle flashes and much more. Alright, now we’re ready to jump into the
effects I showed you at the beginning. By the way, all these effects are from the
Allin1VFX pack on the Unity Asset Store so you can get them there if you wanted, hashtag
not sponsored. So looking at the explosion first you’ll
see there are a lot of objects that make up this effect. What is quite common is to have a parent particle
system that controls the overall effect but doesn’t emit any particles itself, and then
have all the components of the effect as child particle systems that combine to create the
overall visual effect. Each of these objects you see are responsible
for one aspect of the effect. If I isolate the side smoke object you can
see what this particle system is doing. And see it with the full effect, the side
smoke particles are marked in orange. If I pause midway through the effect you will
see the particle count is 25. Each of these little smoke balls is an individual
particle, and so each of these is what we’re controlling using the particle system component. First, let’s look at the emission pane,
you can see rate over time is set to 0, we’re using a burst modifier with a count of 25. This ensures all of the 25 smoke particles
are emitted at the same time. Going to duration, we see it is set to 3. Now because we’re using a burst modifier,
the value for duration doesn't really matter. Remember, duration controls how long the system
emits particles for, but since we just have one burst right at the start this value doesn’t
do anything. Start delay is set to 0, so this particle
system will emit these 25 smoke balls right at the very start. Start lifetime is set to a range of between
1.2 and 1.6. If I click on the arrow on the right you will
see that the option “Random Between Two Constants” is selected. This means that for the 25 particles emitted,
each of them will last for some time between 1.2 seconds and 1.6 seconds before dying. VFX artists will often use random values to
make repeated effects more interesting. If a player is going to see an explosion thousands
of times during the game, adding this randomness to how the particles behave makes it more
interesting and more realistic, since explosions in real life aren’t identical, they all
have their own flavour and personality to them. Notice that because we’re using a burst
emission, this start lifetime controls the length of this particle effect. The maximum lifetime of a particle is 1.6
so this effect will, at most, last roughly 1.6 seconds, before there are no particles
remaining. Start speed is between 3 and 4, which controls
how fast these smoke particles move outwards. If I set this to between 1 and 2, you will
see the particles move a lot slower, and equally if I set the values to 10 and 11, the particles
shoot out much faster. Next, let’s look at the burnmark. This system also uses a burst emissions, but
with a count of 1, since we just want one particle representing the burnmark. Again, duration is mostly irrelevant since
we’re using single emission burst. Start delay is set to 0.1, because burnmarks
don’t happen at the start of the explosion but just after. So this burnmark will appear just slightly
after the effect starts. If I slowly go through the effect you can
see the mark only starts to appear after the smoke has begun to move out. Start lifetime is 2.5 so the burnmark will
last 2 and a half seconds before disappearing. Start speed is set to 0. This makes sense because burnmarks don’t
tend to get up and walk about. They stay in the same place for their lifetime,
so a speed of 0, means the burnmark will not move. The last part of the effect I want to look
at is the late embers part which acts similarly to the other components of the explosion. There is a slight delay before the system
begins emitting, the start lifetime is a random between two constants, so these embers will
last for anywhere between 1.5 seconds and 2.3 seconds and the start speed is between
0.4 and 2. So some of these embers will move at a speed
of 0.4, some will move at 2, and some will move anywhere between 0.4 and 2. The only new part of this effect is that while
we’re using a burst emission, so all the particles are emitted at the same time, the
count is set to between 6 and 10. So each time this explosion effect plays the
number of embers will be anywhere between 6 and 10, again to add some variation and
make the effect more interesting. So that’s the explosion. Next is the lightning strike which only has
one thing I wanted to touch on. And that’s how the strike itself works It’s composed of the standard stuff we’ve
been talking about. It’s a burst emission, with 0 start delay,
the particles last 0.2 seconds and there’s 0 speed because we want the strike to stay
in place. The only thing to note is that you can see
if I pause the system, it still looks like something’s being animated. What’s happening here is that our actual
particle is this orange rectangle shape and we’ve got a texture, which is essentially
just an image, that we’ve put on this particle and we’re scrolling this texture along the
particle to generate a movement-like effect. How to create this effect is outside the scope
of this video, but just keep in mind that the particles emitted from a particle system
are just like you, they can be whatever you want; they’re not limited to circular shapes,
or what you might think a traditional particle might be. They can essentially be anything. Last up is this incineration spell effect. What’s happening in this effect is the pentagram
image on the floor is being animated out. Then some fire effects are rising up before
the whole thing fades. The fire effects are similar to what we’ve
talked about previously. What I want to talk about is the pentagram
image that makes up the core of this effect. If I isolate this system and repeat it a few
times you can see it’s just an image that enlarges a bit before fading. The animating out effect is entirely driven
by ‘over lifetime’ modifiers that you can see down here. If I disable these modifiers this is what’s
left. It’s literally just a single particle with
an image on it. The random rotation is driven by the Start
Rotation modifier here, and if I set this to 0, the effect is almost completely static. To create these kinds of effects you need
to have a burst emission count set to 1. The duration doesn’t matter, the start delay
depends on when you want this to occur and a start speed of 0. The start lifetime, as usual, controls how
long this image stays around for. Once you’ve got this setup, you need to
play with the size over lifetime modifier to replicate the animation-like effect that
causes the image to grow, and the colour over lifetime modifier to control how the colour
of the image changes while it’s alive. These are really powerful modifiers because
they allow you to create these animation-like effects for images, meshes or anything else
you put on a particle. I suggest going into Unity and tweaking the
values for size over lifetime and color over lifetime to see how they impact the particle. And that’s it. Hopefully you have a better understanding
of Unity’s particle system, and how tweaking only a few modifiers drives most of the behaviour
of a visual effect.
