tutorials

Particle Emitter [UED 3]

This tutorial serves as a basic introduction to emitters in UnrealEd 3.0 - Mainly to explore some of the essential emitter properties and how to use them.

What is a particle emitter?

An emitter spawns sprites (flat textures) as "particles" from a point in space. They are used to make a huge range of effects including flames, smoke, jump pad effects, rain, snow, shooting stars, holograms and small insects. There are also MeshEmitters, which can spawn static meshes (not covered in this tutorial).

How to make a new SpriteEmitter

Open the actor browser and select Emitter from the list
Right-click in the 3d viewport window where you want to add the emitter, and click Add Emitter Here
Once the emitter is placed, right-click it and open Emitter Properties
Expand the Emitter tab and click Add
You should see a new item in the list - choose SpriteEmitter from the list and click New

All of the properties for the emitter you just added are listed in the grey boxes. You can add multiple emitters to the same actor you just placed - simply click Add again.

Click preview mode in the 3d viewport and you should see five dots (the default texture) begin to appear. If you want to get rid of all the particles on screen at any time, click Tools > Remove Existing Particles.

Particle system editor

The particle system editor provides a more graphical interface for editing emitters (Tools > Particle Editor). It's good for making effects quickly, however I find it less flexible and more confusing than using the properties window. It has some useful tools such as the emitter wizard, save and load emitter (.emt) files. All the listed properties are the same in both, whatever you find works best . I'll use the emitter properties window in the rest of this tutorial for simplicity.

Customising the emitter properties

Turn real-time preview mode on while viewing the emitter.

Particle Texture

Expand the Texture tab under emitter properties
Select a texture - the best place to find emitter textures is in EmitterTextures.utx and EpicParticles.utx
Go back to the Texture property and click Use

If you change the DrawStyle under the texture tab, you can change the way the texture is displayed. Try some of the different options and see what they do. DrawStyle is set to PTDS_Translucent by default.

Movement
To give the particles basic movement, open the Velocity tab in emitter properties (the grey boxes). Expand StartVelocityRange and look at the X Y and Z min and max boxes.

You can add positive and negative values to tell the particles which way to move along each axis.
Negative values will make a particle move "backward" along an axis and positive values will make a particle move "forward" along an axis.
The bigger the value (+ or -) the faster the particles move.
If your Min and Max values have a big difference between them, there will be a big difference in the speed of individual particles.

Here are the values I added for the first emitter (shown in the animation below):
   X: Max =50
   X: Min =-50
   Y: Max =50
   Y: Max =-50
   Z: Max =100
   Z: Max =100
With these settings the particles move upwards and spread out at an angle.

Acceleration is another way to change the way particles move. It makes particles go faster, slower, or change direction depending on how far they have travelled. For example when I set Acceleration > Z to -100 the particles move up then fall back down like a fountain.

General > MaxParticles sets the number of particles displayed at any one time. It's important for optimisation and creating higher / lower volumes of particles.

Emitter 2

Emitter 1

Scale and Location

At the moment all the particles spawn from the same point in space. You can change it by going to Location > StartLocationRange and setting the X Y and Z, Min and Max values. A large difference in Min and Max values will give the particles a bigger spawning range.

Size > StartSizeRange sets the initial starting size for particles when they spawn. Enter identical values in all the fields to make all the particles the same size, or enter different values to make the particles vary in size. UniformSize controls whether the particles are always the same scale, or if they can stretch along a single axis according to the values entered in StartSizeRange.

Timing
LifetimeRange sets the minimum and maximum length of time (in seconds) each particle should last. Timing together with velocity and acceleration will determine how far the particles travel.

That's the basics covered for this tutorial! The best way to find out how all the properties work is to play around with them, you can make some really interesting effects that way.

A full listing of all the emitter properties and more effects can be found here:
http://udn.epicgames.com/Two/EmittersTopics
http://udn.epicgames.com/Two/EmittersReference#Emitter_Properties