feat(particle): support continuous Birth sub-emitters

packages/core/src/ComponentsManager.ts

@@ -1,6 +1,7 @@
 import { Camera } from "./Camera";
 import { Component } from "./Component";
 import { Renderer } from "./Renderer";
+import { ParticleSystemManager } from "./particle/ParticleSystemManager";
 import { Script } from "./Script";
 import { Animator } from "./animation";
 import { IUICanvas } from "./ui/IUICanvas";
@@ -10,6 +11,8 @@ import { DisorderedArray } from "./utils/DisorderedArray";
  * The manager of the components.
  */
 export class ComponentsManager {
+  /** @internal */
+  readonly _particleSystemManager = new ParticleSystemManager();
   /** @internal */
   _cameraNeedSorting = false;
   /** @internal */

packages/core/src/Engine.ts

@@ -567,6 +567,7 @@ export class Engine extends EventDispatcher {
     for (let i = 0, n = scenes.length; i < n; i++) {
       const scene = scenes[i];
       if (!scene.isActive || scene.destroyed) continue;
+      scene._componentsManager._particleSystemManager.update(deltaTime);
       scene._componentsManager.callRendererOnUpdate(deltaTime);
       scene._updateShaderData();
     }