Initial

resources/app/client/pixi/layers/effects/weather/particles/effect.js

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+/**
+ * An interface for defining particle-based weather effects
+ * @param {PIXI.Container} parent     The parent container within which the effect is rendered
+ * @param {object} [options]          Options passed to the getParticleEmitters method which can be used to customize
+ *                                    values of the emitter configuration.
+ * @interface
+ */
+class ParticleEffect extends FullCanvasObjectMixin(PIXI.Container) {
+  constructor(options={}) {
+    super();
+    /**
+     * The array of emitters which are active for this particle effect
+     * @type {PIXI.particles.Emitter[]}
+     */
+    this.emitters = this.getParticleEmitters(options);
+  }
+
+  /* -------------------------------------------- */
+
+  /**
+   * Create an emitter instance which automatically updates using the shared PIXI.Ticker
+   * @param {PIXI.particles.EmitterConfigV3} config   The emitter configuration
+   * @returns {PIXI.particles.Emitter}                The created Emitter instance
+   */
+  createEmitter(config) {
+    config.autoUpdate = true;
+    config.emit = false;
+    return new PIXI.particles.Emitter(this, config);
+  }
+
+  /* -------------------------------------------- */
+
+  /**
+   * Get the particle emitters which should be active for this particle effect.
+   * This base class creates a single emitter using the explicitly provided configuration.
+   * Subclasses can override this method for more advanced configurations.
+   * @param {object} [options={}] Options provided to the ParticleEffect constructor which can be used to customize
+   *                              configuration values for created emitters.
+   * @returns {PIXI.particles.Emitter[]}
+   */
+  getParticleEmitters(options={}) {
+    if ( foundry.utils.isEmpty(options) ) {
+      throw new Error("The base ParticleEffect class may only be used with an explicitly provided configuration");
+    }
+    return [this.createEmitter(/** @type {PIXI.particles.EmitterConfigV3} */ options)];
+  }
+
+  /* -------------------------------------------- */
+
+  /** @override */
+  destroy(...args) {
+    for ( const e of this.emitters ) e.destroy();
+    this.emitters = [];
+    super.destroy(...args);
+  }
+
+  /* -------------------------------------------- */
+
+  /**
+   * Begin animation for the configured emitters.
+   */
+  play() {
+    for ( let e of this.emitters ) {
+      e.emit = true;
+    }
+  }
+
+  /* -------------------------------------------- */
+
+  /**
+   * Stop animation for the configured emitters.
+   */
+  stop() {
+    for ( let e of this.emitters ) {
+      e.emit = false;
+    }
+  }
+}

resources/app/client/pixi/layers/effects/weather/particles/leaves.js

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+/**
+ * A full-screen weather effect which renders gently falling autumn leaves.
+ * @extends {ParticleEffect}
+ */
+class AutumnLeavesWeatherEffect extends ParticleEffect {
+
+  /** @inheritdoc */
+  static label = "WEATHER.AutumnLeaves";
+
+  /**
+   * Configuration for the particle emitter for falling leaves
+   * @type {PIXI.particles.EmitterConfigV3}
+   */
+  static LEAF_CONFIG = {
+    lifetime: {min: 10, max: 10},
+    behaviors: [
+      {
+        type: "alpha",
+        config: {
+          alpha: {
+            list: [{time: 0, value: 0.9}, {time: 1, value: 0.5}]
+          }
+        }
+      },
+      {
+        type: "moveSpeed",
+        config: {
+          speed: {
+            list: [{time: 0, value: 20}, {time: 1, value: 60}]
+          },
+          minMult: 0.6
+        }
+      },
+      {
+        type: "scale",
+        config: {
+          scale: {
+            list: [{time: 0, value: 0.2}, {time: 1, value: 0.4}]
+          },
+          minMult: 0.5
+        }
+      },
+      {
+        type: "rotation",
+        config: {accel: 0, minSpeed: 100, maxSpeed: 200, minStart: 0, maxStart: 365}
+      },
+      {
+        type: "textureRandom",
+        config: {
+          textures: Array.fromRange(6).map(n => `ui/particles/leaf${n + 1}.png`)
+        }
+      }
+    ]
+  };
+
+  /* -------------------------------------------- */
+
+  /** @inheritdoc */
+  getParticleEmitters() {
+    const d = canvas.dimensions;
+    const maxParticles = (d.width / d.size) * (d.height / d.size) * 0.25;
+    const config = foundry.utils.deepClone(this.constructor.LEAF_CONFIG);
+    config.maxParticles = maxParticles;
+    config.frequency = config.lifetime.min / maxParticles;
+    config.behaviors.push({
+      type: "spawnShape",
+      config: {
+        type: "rect",
+        data: {x: d.sceneRect.x, y: d.sceneRect.y, w: d.sceneRect.width, h: d.sceneRect.height}
+      }
+    });
+    return [this.createEmitter(config)];
+  }
+}