Rendering Lines on Top of HTML Images in Three.js

Based on your issue, it appears you're facing a rendering order problem where your Three.js lines are being rendered behind your HTML image element. This is a common challenge when mixing HTML elements with WebGL content.

Possible Solutions

1. Use Line2 with Depth Testing Disabled

The Line2 class from Three.js can be used with a LineMaterial that has depth testing disabled:

JAVASCRIPTCopied
import { Line2 } from 'three/examples/jsm/lines/Line2.js';
import { LineGeometry } from 'three/examples/jsm/lines/LineGeometry.js';
import { LineMaterial } from 'three/examples/jsm/lines/LineMaterial.js';

// Create line geometry
const lineGeometry = new LineGeometry();
lineGeometry.setPositions([x1, y1, z1, x2, y2, z2]); // Your line coordinates

// Create line material with depthTest disabled
const lineMaterial = new LineMaterial({
  color: 0x0000ff,
  linewidth: 3, // Width in pixels
  vertexColors: false,
  dashed: false,
  depthTest: false, // This is key - disable depth testing
  depthWrite: false // Also disable depth writing
});

// Create the line
const line = new Line2(lineGeometry, lineMaterial);
scene.add(line);

2. Adjust Rendering Order

You can also try setting a higher renderOrder value for your lines:

JAVASCRIPTCopied
line.renderOrder = 1; // Higher values render later (on top)

3. Position the Lines Slightly in Front

Another approach is to position your lines slightly in front of the plane where your image is:

JAVASCRIPTCopied
// If your image is at z=0, place lines at a slightly negative z value
line.position.z = -0.01;

4. Use CSS 3D Renderer for the Lines

If you're already using HTML elements, you might consider using CSS3DRenderer for your lines as well, which would naturally integrate with the HTML rendering order.

Additional Considerations

• Make sure your camera's near plane isn't set too far from the origin, which could cause rendering issues with closely positioned objects.
• If using LineSegments2 or LineSegmentsGeometry, the same principles apply regarding depth testing and render order.
• Consider using a different approach for your product image, such as using a textured plane in Three.js instead of an HTML element, which would give you more control over the rendering order.

Let me know if you need more specific guidance based on your implementation details!