[THREEJS] GLB 모델 리소스 제거

class ResourceTracker {
  constructor() {
    this.resources = new Set();
  }
  track(resource) {
    if (!resource) {
      return resource;
    }

    // handle children and when material is an array of materials or
    // uniform is array of textures
    if (Array.isArray(resource)) {
      resource.forEach(resource => this.track(resource));
      return resource;
    }

    if (resource.dispose || resource instanceof THREE.Object3D) {
      this.resources.add(resource);
    }
    if (resource instanceof THREE.Object3D) {
      this.track(resource.geometry);
      this.track(resource.material);
      this.track(resource.children);
    } else if (resource instanceof THREE.Material) {
      // We have to check if there are any textures on the material
      for (const value of Object.values(resource)) {
        if (value instanceof THREE.Texture) {
          this.track(value);
        }
      }
      // We also have to check if any uniforms reference textures or arrays of textures
      if (resource.uniforms) {
        for (const value of Object.values(resource.uniforms)) {
          if (value) {
            const uniformValue = value.value;
            if (uniformValue instanceof THREE.Texture ||
              Array.isArray(uniformValue)) {
              this.track(uniformValue);
            }
          }
        }
      }
    }
    return resource;
  }
  untrack(resource) {
    this.resources.delete(resource);
  }
  dispose() {
    for (const resource of this.resources) {
      if (resource instanceof THREE.Object3D) {
        if (resource.parent) {
          resource.parent.remove(resource);
        }
      }
      if (resource.dispose) {
        resource.dispose();
      }
    }
    this.resources.clear();
  }
}

function waitSeconds(seconds = 0) {
  return new Promise(resolve => setTimeout(resolve, seconds * 1000));
}

          async function loadBackgrounds() {
            for (;;) {
              for (const url of backgroundfileURLs) {
                const resMgr = new ResourceTracker();
                const track = resMgr.track.bind(resMgr);
                const background = await loadBackgroundUsingPromise(url);
                
                const geometry = new THREE.PlaneGeometry(1, 1);
                const material = track(new THREE.MeshBasicMaterial({ map: background, side: THREE.DoubleSide }));
                const plane = track(new THREE.Mesh(geometry, material));

                plane.scale.set(800, 800)
                plane.position.set(0, -200, -200)
                plane.rotation.set(0,-0.5,0)
                back.add(plane)
                scene.add(back)
                
                // 모델 지속 시간(초)
                await waitSeconds(3);

                // 리소스 제거
                resMgr.dispose();
                
                // 모델 사라진 시간(초)
                //await waitSeconds(1);
              }
            }
          }