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When you see one of the following in a game, then a particle system is likely behind it:
These things typically cannot be modeled by meshes. In very simple terms:
Particle effects can be animated (e.g. sparks, drops) and static (strands of grass, hair). Non-particle effects include bloom/glow, and motion blur/afterimage. In this tutorial we will look at animated particles (com.jme3.effect).
package jme3test.helloworld; import com.jme3.app.SimpleApplication; import com.jme3.effect.ParticleEmitter; import com.jme3.effect.ParticleMesh; import com.jme3.material.Material; import com.jme3.math.ColorRGBA; import com.jme3.math.Vector3f; /** Sample 11 - how to create fire, water, and explosion effects. */ public class HelloEffects extends SimpleApplication { public static void main(String[] args) { HelloEffects app = new HelloEffects(); app.start(); } @Override public void simpleInitApp() { ParticleEmitter fire = new ParticleEmitter("Emitter", ParticleMesh.Type.Triangle, 30); Material mat_red = new Material(assetManager, "Common/MatDefs/Misc/Particle.j3md"); mat_red.setTexture("Texture", assetManager.loadTexture("Effects/Explosion/flame.png")); fire.setMaterial(mat_red); fire.setImagesX(2); fire.setImagesY(2); // 2x2 texture animation fire.setEndColor( new ColorRGBA(1f, 0f, 0f, 1f)); // red fire.setStartColor(new ColorRGBA(1f, 1f, 0f, 0.5f)); // yellow fire.setInitialVelocity(new Vector3f(0, 2, 0)); fire.setStartSize(1.5f); fire.setEndSize(0.1f); fire.setGravity(0); fire.setLowLife(0.5f); fire.setHighLife(3f); fire.setVelocityVariation(0.3f); rootNode.attachChild(fire); ParticleEmitter debris = new ParticleEmitter("Debris", ParticleMesh.Type.Triangle, 10); Material debris_mat = new Material(assetManager, "Common/MatDefs/Misc/Particle.j3md"); debris_mat.setTexture("Texture", assetManager.loadTexture("Effects/Explosion/Debris.png")); debris.setMaterial(debris_mat); debris.setImagesX(3); debris.setImagesY(3); // 3x3 texture animation debris.setRotateSpeed(4); debris.setSelectRandomImage(true); debris.setInitialVelocity(new Vector3f(0, 4, 0)); debris.setStartColor(new ColorRGBA(1f, 1f, 1f, 1f)); debris.setGravity(6f); debris.setVelocityVariation(.60f); rootNode.attachChild(debris); debris.emitAllParticles(); } }
You should see an explosion that sends debris flying, and a fire. More example code
Start by choosing a material texture for your effect. If you provide the emitter with a set of textures (see image), it can use them either for variation (random order), or as animation steps (fixed order).
Setting emitter textures works just as you have already learned in previous chapters. This time we use the Particle.j3md
default material. In the following example, we have a closer look at the Debris effect.
... Material debris_mat = new Material(assetManager, "Common/MatDefs/Misc/Particle.j3md"); debris_mat.setTexture("Texture", assetManager.loadTexture("Effects/Explosion/Debris.png")); debris.setMaterial(debris_mat); debris.setImagesX(3); // columns debris.setImagesY(3); // rows debris.setSelectRandomImage(true); ...
As you see in the debris example, texture animations improve effects because each "flame" or "piece of debris" looks different. Also think of electric or magic effects, where you can create very interesting animations by using an ordered morphing series of lightning bolts; or flying leaves or snow flakes, for instance.
The following effect textures are some of the example textures included in test-data.jar
.
Texture Path | Dimension | Preview |
---|---|---|
Effects/Explosion/Debris.png | 3*3 | ![]() |
Effects/Explosion/flame.png | 2*2 | ![]() |
Effects/Explosion/shockwave.png | 1*1 | ![]() |
Effects/Explosion/smoketrail.png | 1*3 | ![]() |
Effects/Smoke/Smoke.png | 1*15 | ![]() |
Copy them into you assets/Effects
directory to use them.
For your game, you will likely create custom textures. Look at the fire example again.
ParticleEmitter fire = new ParticleEmitter("Emitter", ParticleMesh.Type.Triangle, 30); Material mat_red = new Material(assetManager, "Common/MatDefs/Misc/Particle.j3md"); mat_red.setTexture("m_Texture", assetManager.loadTexture("Effects/Explosion/flame.png")); fire.setMaterial(mat_red); fire.setImagesX(2); // columns fire.setImagesY(2); // rows fire.setEndColor( new ColorRGBA(1f, 0f, 0f, 1f)); // red fire.setStartColor(new ColorRGBA(1f, 1f, 0f, 0.5f)); // yellow
Create a grayscale texture in a graphic editor, and save it to your assets/Effects
directory. If you split up one image file into x*y animation steps, make sure each animation step is of equal size–just as you see in the examples here.
A particle system is always centered around an emitter.
Use the setShape()
method to change the EmitterShape:
Example: emitter.setShape(new EmitterPointShape(Vector3f.ZERO));
You create different effects by changing the emitter parameters:
Parameter | Method (default value) | Description |
---|---|---|
number | setNumParticles() | The maximum number of particles visible at the same time. Value is specified by user in constructor. |
velocity | setInitialVelocity() (Vector3f.ZERO) | You must specify a vector how fast particles should move and it which start direction. |
direction | setVelocityVariation() (0.2f) setFacingVelocity() (false) setRandomAngle() (false) setFaceNormal() (Vector3f.NAN) setRotateSpeed() (0f) | Optional accessors that control in which direction particles face when flying. |
lifetime | setLowLife() (3f) setHighLife() (7f) | Minimum and maximum time period before particles fade. |
emission rate | setParticlesPerSec() (20) | How many new particles are emitted per second. |
color | setStartColor() setEndColor() (gray) | Set to two different colors for gradient effects, or to same color. |
size | setStartSize() (0.2f) setEndSize() (2f) | Set to two different values for shrink/grow effect, or to same size. |
gravity | setGravity() (0.1f) | Whether particles falls down eventually. Set to 0f for zero-g effects. |
You can find details about effect parameters in the user guide. Add and modify one paramter at a time, and try different values until you get the effect you want. Tip: Use the jMonkeyPlatform SceneComposer to preview effects settings (instructions: TODO).
Can you "invert" the campfire into a small waterfall?
You have learned that many different effects can be created by changing the parameters and textures of one general emitter object.
Now we move on to the next exciting chapter – the simulation of physical objects. Let's shoot some cannon balls at a brick wall!