Fireburst.java

import processing.core.PApplet;

import java.util.HashSet;
import java.util.Set;
import java.util.stream.Collectors;

public class Fireburst extends PApplet {
	private Set<FlameGenerator> generators;

	public static void main(String args[]) {
		PApplet.main("Fireburst");
	}

	@Override
	public void settings() {
		size(800, 600);
	}

	@Override
	public void setup() {
		clear();
		generators = new HashSet<>();
		generators.add(new FlameGenerator(width*0.33f, height*0.2f));
		generators.add(new FlameGenerator(width*0.5f, height*0.3f));
		generators.add(new FlameGenerator(width*0.66f, height*0.4f));

		colorMode(HSB);
	}

	@Override
	public void draw() {
		fill(50, 0, 0, 60);
		rect(0, 0, width, height);
		generators.forEach(FlameGenerator::update);
		generators.forEach(
				generator -> generator
						.particles
						.stream()
						.sorted((p1, p2) -> Float.compare(p1.position.z, p2.position.y))
						.forEach(this::drawParticle)
		);
	}

	private void drawParticle(Particle particle) {
		noStroke();
		fill(map(particle.lifetime(), 0, 1, 0, 50), 255, 255, map(particle.lifetime(), 0, 1, 255, 0));
		float size = particle.size + cos(particle.age * 0.04f) * particle.position.x * 0.1f * (1-particle.lifetime());
		ellipse(particle.spawnPosition.x + sin(particle.age * 0.04f) * particle.position.x, particle.position.y + particle.spawnPosition.y, size, size);
	}

	private static class Vector3 {
		float x;
		float y;
		float z;
		Vector3(float x, float y, float z) {
			this.x = x;
			this.y = y;
			this.z = z;
		}
	}

	private class Particle {
		Vector3 position;
		Vector3 velocity;
		Vector3 spawnPosition;
		int age;
		float size;
		int maxAge;

		Particle(Vector3 position, Vector3 velocity) {
			this.spawnPosition = position;
			this.position = new Vector3(0,0,0);
			this.velocity = velocity;
			this.age = 0;
			this.size = 8;
			this.maxAge = (int)random(80, 200);
		}

		void update() {
			position.x += velocity.x;
			position.y += velocity.y;
			position.z += velocity.z;
			age += 1;
			position.x += random(-1f, 1f);
			velocity.y *= 0.99f;
			velocity.x *= 0.99f;
			velocity.z *= 0.99f;
		}

		float lifetime() {
			return map(age, 0, maxAge, 0, 1);
		}

		boolean isAlive() {
			return age < maxAge;
		}
	}

	private class FlameGenerator {
		final float x;
		final float y;
		Set<Particle> particles;

		private FlameGenerator(float x, float y) {
			this.x = x;
			this.y = y;
			particles = new HashSet<>();
		}

		void update() {
			Vector3 particleVelocity = new Vector3(random(-0.5f, 0.5f), random(0.5f, 4f), random(-0.01f, 0.01f));
			particles.add(new Particle(new Vector3(x + random(8), y + random(4), 0), particleVelocity));
			particles.forEach(Particle::update);

			particles = particles.stream().filter(Particle::isAlive).collect(Collectors.toSet());
		}
	}
}