feat(particle): add collection clear APIs

packages/core/src/particle/modules/CustomDataModule.ts

@@ -186,6 +186,18 @@ export class CustomDataModule extends ParticleGeneratorModule {
     this._gradients.delete(name);
   }
 
+  /**
+   * Remove all custom data streams.
+   */
+  clear(): void {
+    for (const name of this._curves.keys()) {
+      this.removeCurve(name);
+    }
+    for (const name of this._gradients.keys()) {
+      this.removeGradient(name);
+    }
+  }
+
   /**
    * @internal
    */

packages/core/src/particle/modules/SubEmittersModule.ts

@@ -95,6 +95,17 @@ export class SubEmittersModule extends ParticleGeneratorModule {
     this._generator._setTransformFeedback();
   }
 
+  /**
+   * Remove all sub-emitter slots.
+   */
+  clear(): void {
+    if (this._subEmitters.length === 0) {
+      return;
+    }
+    this._subEmitters.length = 0;
+    this._generator._setTransformFeedback();
+  }
+
   override get enabled(): boolean {
     return this._enabled && this._generator._renderer.engine._hardwareRenderer.isWebGL2;
   }

tests/src/core/particle/CustomData.test.ts

@@ -163,6 +163,17 @@ describe("CustomDataModule", function () {
     expect(customData.gradients.size).to.eq(0);
   });
 
+  it("clear removes every stream", function () {
+    const customData = particleRenderer.generator.customData;
+    customData.addCurve("A", new ParticleCompositeCurve(1));
+    customData.addGradient("B", new ParticleCompositeGradient(new Color()));
+
+    customData.clear();
+
+    expect(customData.curves.size).to.eq(0);
+    expect(customData.gradients.size).to.eq(0);
+  });
+
   it("removeCurve / removeGradient zero out shaderData uniforms", function () {
     const customData = particleRenderer.generator.customData;
     const shaderData = particleRenderer.shaderData;

tests/src/core/particle/SubEmitter.test.ts

@@ -90,6 +90,23 @@ describe("SubEmitter", () => {
     child.entity.destroy();
   });
 
+  it("clear removes every sub-emitter slot", () => {
+    const parent = createParticleRenderer(engine, "Parent_Clear");
+    const child = createParticleRenderer(engine, "Child_Clear");
+
+    parent.generator.subEmitters.enabled = true;
+    parent.generator.subEmitters.addSubEmitter(child, ParticleSubEmitterType.Death);
+    expect((parent.generator as any)._useTransformFeedback).to.equal(true);
+
+    parent.generator.subEmitters.clear();
+
+    expect(parent.generator.subEmitters.subEmitters).to.have.length(0);
+    expect((parent.generator as any)._useTransformFeedback).to.equal(false);
+
+    parent.entity.destroy();
+    child.entity.destroy();
+  });
+
   it("Sub system's own EmissionModule does not double-fire when sub-emit drives it", () => {
     // The target renderer has its own t=0 burst AND is auto-playing on enable.
     // The slot must NOT read that burst and re-fire — sub system's own emission