Combining AR and Stereoscopic Rendering in Three.js

Based on the information available, you're trying to create a hybrid AR/VR experience where you have AR functionality (camera feed with 3D objects) but with stereoscopic rendering for Google Cardboard. This is an interesting challenge that involves aspects of both AR and VR.

Understanding the Issue

When you switched from the VR button to the AR button, you lost the stereoscopic rendering capability that's built into the VR mode. This is because:

1. The VR button utilizes WebXR's VR mode which automatically handles stereoscopic rendering
2. The AR button uses WebXR's AR mode which is typically designed for a single camera view (non-stereoscopic)

Potential Solution

You might need to implement a custom solution that combines both functionalities. Here are some approaches to consider:

1. Use the StereoCamera class from Three.js to create stereoscopic rendering while maintaining AR functionality
2. Modify your WebXRManager configuration to support both AR features and stereoscopic rendering

Using StereoCamera

The StereoCamera class is designed specifically for stereoscopic rendering and could be used alongside your AR implementation:

JAVASCRIPTCopied
// Create a stereo camera
const stereoCamera = new THREE.StereoCamera();
stereoCamera.eyeSep = 0.064; // Eye separation, adjust as needed

// In your render loop
function render() {
  // Update the stereo camera based on your main camera
  stereoCamera.update(mainCamera);
  
  // Render left eye
  renderer.setViewport(0, 0, width/2, height);
  renderer.render(scene, stereoCamera.cameraL);
  
  // Render right eye
  renderer.setViewport(width/2, 0, width/2, height);
  renderer.render(scene, stereoCamera.cameraR);
}

Custom WebXR Implementation

You might need to create a custom implementation that combines AR and VR features:

JAVASCRIPTCopied
// Initialize WebXR with custom features
const xrButton = document.createElement('button');
xrButton.addEventListener('click', onXRButtonClick);

function onXRButtonClick() {
  // Request a session with both AR and VR features
  navigator.xr.requestSession('immersive-ar', {
    optionalFeatures: ['local-floor', 'bounded-floor', 'hand-tracking']
  }).then(onSessionStarted);
}

function onSessionStarted(session) {
  // Configure session for stereoscopic rendering
  // This part would require custom implementation
  // ...
}

Limitations

It's important to note that combining AR and stereoscopic VR in this way may have limitations:

1. WebXR's AR and VR modes are typically separate, and combining them might require workarounds
2. Performance might be an issue, especially on mobile devices
3. The WebXRManager in Three.js might need custom modifications to support this hybrid approach

Next Steps

You might want to explore the WebXRManager documentation in more detail to understand how to customize the XR experience. Additionally, looking at examples of custom stereoscopic rendering in Three.js could provide insights for your implementation.

The approach will likely require some experimentation and custom code beyond the standard Three.js examples, but it should be technically possible to achieve what you're looking for.