Add onPostFrame in Pass, ScreenPass and RenderManager that is triggered post frame.

src/postprocessing/Pass.ts

 
     onRegister?(renderer: IRenderManager): void;
     onUnregister?(renderer: IRenderManager): void;
+
+    onPostFrame?(renderManager: IRenderManager): void;
+
 }

src/postprocessing/ScreenPass.ts

     reRender(renderer: IWebGLRenderer, writeBuffer?: WebGLMultipleRenderTargets | WebGLRenderTarget | null, deltaTime?: number, maskActive?: boolean) {
         if (this._lastReadBuffer) this.render(renderer, writeBuffer, this._lastReadBuffer, deltaTime, maskActive)
     }
+    private _needsReRender = false
+    onPostFrame(renderManager: IRenderManager) {
+        if (!this._needsReRender) return
+        this._needsReRender = false
+        this.reRender(renderManager.renderer)
+    }
 
     dispose() {
         this._lastReadBuffer = undefined

src/rendering/RenderManager.ts

             this.refreshPasses()
         }
         for (const pass of this._passes) {
-            if (pass.enabled) pass.beforeRender?.(scene, scene.mainCamera, this)
+            if (pass.enabled && pass.beforeRender) pass.beforeRender(scene, scene.mainCamera, this)
         }
         this._composer.render()
         this._frameCount += 1
         this._dirty = false
     }
 
+    onPostFrame = () => {
+        for (const pass of this._passes) {
+            if (pass.enabled && pass.onPostFrame) pass.onPostFrame?.(this)
+        }
+    }
+
     get needsRender(): boolean {
         this._dirty = this._dirty || this._passes.findIndex(value => value.dirty) >= 0 // todo: check for enabled passes only.
         return this._dirty

src/three/utils/index.ts

 export {dataTextureFromColor, dataTextureFromVec4, halfFloatToRgbe} from './conversion'
 export {uniform, matDefine} from './decorators'
 export {getEncodingComponents, getTexelEncoding, getTexelDecoding, getTexelDecoding2, getTexelDecodingFunction, getTexelEncodingFunction, getTextureColorSpaceFromMap} from './encoding'
-export {generateUUID, toIndexedGeometry} from './misc'
+export {generateUUID, toIndexedGeometry, isInScene} from './misc'
 export {getTextureDataType, textureToCanvas, textureDataToImageData, textureToDataUrl, texImageToCanvas} from './texture'
 export {threeConstMappings} from './const-mappings'
 

src/viewer/ThreeViewer.ts

             }
 
             this.dispatchEvent({type: 'postFrame', target: this})
+            this.renderManager.onPostFrame()
 
             if (!needsRender) // break if no frame rendered
                 break