Is there any way to make the background of a 3D-model transparent in a-scene in ionic?

问题

My problem is to how make the white background of a-frame transparent that we just can see whatever we see from the iPhone camera plus the 3D-model.

I have been trying to make AR (Augmented Reality) working in Ionic iOS version. I realised that a-frame can not trigger webcam for some reasons in iOS. So one of the workaround came to my mind is to load 3D model by a-frame and and trigger the camera at the same time. This some how works, in 2/3 of the screen we can see the camera input and 1/3 the model is loaded with white background. If I can transparent the background of the model then at I would be very happy. Is there any way to make the background of the model transparent in Ionic? is there any other workaround for this problem?

what I have in home.page.html is simply: ` Ionic Blank

<ion-content>
 <a-scene  *ngIf="iosReady"
       renderer="alpha: true;
               colorManagement: true;
               sortObjects: true;
               physicallyCorrectLights: true;
               maxCanvasWidth: 1920;
               maxCanvasHeight: 1920;">
  <a-gltf-model  position="1 1 -4" 
       src="/assets/models/LibertStatue.gltf" ></a-gltf-model>
 </a-scene>
</ion-content>`

And in home.page.ts I have:

const cameraPreviewOpts: CameraPreviewOptions = {
            x: 0,
            y: 0,
            width: window.screen.width,
            height: window.screen.height,
            camera: 'rear',
            tapPhoto: true,
            previewDrag: true,
            toBack: true,
            alpha: 1
        }


        CameraPreview.startCamera(cameraPreviewOpts).then(
            (res) => {
                console.log(res);
            },
            (err) => {
                console.log(err);
            });
    });

来源：https://stackoverflow.com/questions/56164300/is-there-any-way-to-make-the-background-of-a-3d-model-transparent-in-a-scene-in