CSS3DRenderer and StereoEffect Compatibility Issue

The error you're encountering, "renderer.clear is not a function," occurs because the StereoEffect class is designed to work with the WebGLRenderer, not with the CSS3DRenderer.

Why This Error Occurs

The StereoEffect internally calls methods like renderer.clear() which are specific to the WebGLRenderer class. As shown in the documentation:

• WebGLRenderer has a .clear() method that clears color, depth, or stencil drawing buffers
• WebGLRenderer also has specialized methods like .clearStencil()
• CSS3DRenderer doesn't implement these methods as it works with DOM elements rather than WebGL buffers

Possible Solutions

1. Use WebGLRenderer instead: If stereo effect is essential, you'll need to use the WebGLRenderer instead of CSS3DRenderer.

2. Create a custom wrapper: You could create a wrapper for CSS3DRenderer that implements dummy versions of the methods StereoEffect expects:

JAVASCRIPTCopied
// Custom wrapper for CSS3DRenderer
class CSS3DRendererWrapper {
    constructor() {
        this.cssRenderer = new CSS3DRenderer();
        this.domElement = this.cssRenderer.domElement;
    }
    
    // Implement dummy methods expected by StereoEffect
    clear() {
        // No-op function
        return;
    }
    
    setSize(width, height) {
        this.cssRenderer.setSize(width, height);
    }
    
    render(scene, camera) {
        this.cssRenderer.render(scene, camera);
    }
}

// Usage
renderer = new CSS3DRendererWrapper();
effect = new StereoEffect(renderer);

3. Modify StereoEffect: Create a custom version of StereoEffect that works with CSS3DRenderer by removing calls to methods that don't exist.

Recommendation

The most straightforward approach would be to use WebGLRenderer instead of CSS3DRenderer if you need stereo effects. If you specifically need CSS3D capabilities, you might need to implement your own stereo effect solution that's compatible with CSS3DRenderer, or modify the existing StereoEffect class to check for method existence before calling them.