feat(particle): support continuous Birth sub-emitters

e2e/case/.mockForE2E.ts

@@ -14,6 +14,25 @@ export const updateForE2E = (engine, deltaTime = 100, loopTime = 10) => {
   engine._hardwareRenderer._gl.finish();
 };
 
+export const updateForE2EAsync = async (engine, deltaTime = 100, loopTime = 10) => {
+  engine._vSyncCount = Infinity;
+  engine._time._lastSystemTime = 0;
+  let times = 0;
+  performance.now = function () {
+    times++;
+    return times * deltaTime;
+  };
+  for (let i = 0; i < loopTime; ++i) {
+    engine.update();
+    engine._hardwareRenderer._gl.finish();
+    await new Promise<void>((resolve) => setTimeout(resolve, 0));
+  }
+  const currentTime = times * deltaTime;
+  performance.now = () => currentTime;
+  engine.update();
+  engine._hardwareRenderer._gl.finish();
+};
+
 let screenshotCanvas: HTMLCanvasElement = null;
 let flipYCanvas: HTMLCanvasElement = null;
 

e2e/case/particleRenderer-sub-emitter.ts

@@ -29,7 +29,7 @@ import {
   Texture2D,
   WebGLEngine
 } from "@galacean/engine";
-import { initScreenshot, updateForE2E } from "./.mockForE2E";
+import { initScreenshot, updateForE2EAsync } from "./.mockForE2E";
 
 WebGLEngine.create({
   canvas: "canvas"
@@ -48,9 +48,9 @@ WebGLEngine.create({
       url: "https://mdn.alipayobjects.com/huamei_b4l2if/afts/img/A*JPsCSK5LtYkAAAAAAAAAAAAADil6AQ/original",
       type: AssetType.Texture
     })
-    .then((texture) => {
+    .then(async (texture) => {
       createSubEmitterScene(engine, rootEntity, <Texture2D>texture);
-      updateForE2E(engine, 50, 14);
+      await updateForE2EAsync(engine, 50, 14);
       initScreenshot(engine, camera);
     });
 });

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();
     }

packages/core/src/graphic/Buffer.ts

@@ -1,7 +1,7 @@
 import { GraphicsResource } from "../asset/GraphicsResource";
 import { TypedArray } from "../base";
 import { Engine } from "../Engine";
-import { IPlatformBuffer } from "../renderingHardwareInterface";
+import { IPlatformBuffer, IPlatformBufferReadback } from "../renderingHardwareInterface";
 import { UpdateFlagManager } from "../UpdateFlagManager";
 import { BufferBindFlag } from "./enums/BufferBindFlag";
 import { BufferUsage } from "./enums/BufferUsage";
@@ -239,6 +239,11 @@ export class Buffer extends GraphicsResource {
     this._platformBuffer.copyFromBuffer(srcBuffer._platformBuffer, srcByteOffset, dstByteOffset, byteLength);
   }
 
+  /** @internal */
+  _createReadback(): IPlatformBufferReadback {
+    return this._platformBuffer.createReadback();
+  }
+
   /**
    * Mark buffer as readable, the `data` property will be not accessible anymore.
    */

packages/core/src/particle/ParticleBufferUtils.ts

@@ -17,12 +17,18 @@ import { ParticleInstanceVertexAttribute } from "./enums/attributes/ParticleInst
  */
 export class ParticleBufferUtils {
   static readonly feedbackVertexStride = 24;
+  static readonly trajectoryFeedbackVertexStride = 48;
 
   static readonly feedbackVertexElements = [
     new VertexElement(ParticleFeedbackVertexAttribute.Position, 0, VertexElementFormat.Vector3, 0),
     new VertexElement(ParticleFeedbackVertexAttribute.Velocity, 12, VertexElementFormat.Vector3, 0)
   ];
 
+  static readonly trajectoryFeedbackVertexElements = [
+    ...ParticleBufferUtils.feedbackVertexElements,
+    new VertexElement(ParticleFeedbackVertexAttribute.WorldPosition, 24, VertexElementFormat.Vector3, 0)
+  ];
+
   static readonly feedbackInstanceElements = [
     new VertexElement(ParticleInstanceVertexAttribute.ShapePositionStartLifeTime, 0, VertexElementFormat.Vector4, 0),
     new VertexElement(ParticleInstanceVertexAttribute.DirectionTime, 16, VertexElementFormat.Vector4, 0),
@@ -32,15 +38,19 @@ export class ParticleBufferUtils {
     new VertexElement(ParticleInstanceVertexAttribute.Random1, 92, VertexElementFormat.Vector4, 0),
     new VertexElement(ParticleInstanceVertexAttribute.SimulationWorldPosition, 108, VertexElementFormat.Vector3, 0),
     new VertexElement(ParticleInstanceVertexAttribute.SimulationWorldRotation, 120, VertexElementFormat.Vector4, 0),
-    new VertexElement(ParticleInstanceVertexAttribute.Random2, 152, VertexElementFormat.Vector4, 0)
+    new VertexElement(ParticleInstanceVertexAttribute.Random2, 152, VertexElementFormat.Vector4, 0),
+    new VertexElement(ParticleInstanceVertexAttribute.InheritVelocityRandom, 168, VertexElementFormat.Float, 0)
   ];
 
-  static readonly instanceVertexStride = 168;
+  static readonly instanceVertexStride = 172;
   static readonly instanceVertexFloatStride = ParticleBufferUtils.instanceVertexStride / 4;
 
   static readonly startLifeTimeOffset = 3;
   static readonly timeOffset = 7;
   static readonly simulationUVOffset = 34;
+  static readonly inheritVelocityRandomOffset = 42;
+  static readonly feedbackWorldPositionOffset = 6;
+  static readonly feedbackTrajectoryVelocityOffset = 9;
 
   static readonly billboardIndexCount = 6;