Highlighting Line2 Objects in Three.js

When working with Line2 objects in Three.js, you might encounter challenges when trying to use the OutlinePass post-processing effect to highlight them. This is because OutlinePass is primarily designed to work with mesh-based objects rather than line-based objects.

Alternative Approaches

Since OutlinePass may not work effectively with Line2 objects, here are some alternative approaches you can consider:

1. Custom Line Material: Create a custom LineMaterial with a higher linewidth or different color to highlight the line:

JAVASCRIPTCopied
// Original line
const normalMaterial = new THREE.LineMaterial({
    color: 0x0000ff,
    linewidth: 2
});

// Highlighted version
const highlightMaterial = new THREE.LineMaterial({
    color: 0xff0000,  // Different color
    linewidth: 4      // Thicker line
});

// Switch materials to highlight
myLine.material = highlightMaterial;

2. Duplicate Line: Create a slightly larger duplicate line behind your original line:

JAVASCRIPTCopied
// Create a duplicate line with larger width for highlighting
const highlightLine = new THREE.Line2(originalLine.geometry.clone(), 
    new THREE.LineMaterial({
        color: 0xffff00,
        linewidth: originalLine.material.linewidth + 2
    })
);

// Position it exactly like the original
highlightLine.position.copy(originalLine.position);
highlightLine.rotation.copy(originalLine.rotation);
highlightLine.scale.copy(originalLine.scale);

// Add to scene when you want to highlight
scene.add(highlightLine);

3. Custom Shader: Implement a custom shader for your LineMaterial that can toggle a highlight effect.

4. Use EffectComposer with Custom Passes: While OutlinePass might not work directly, you could create a custom pass using EffectComposer that specifically targets line geometries.

Remember that Line2, LineGeometry, and LineMaterial are part of the examples in Three.js and provide more features than the basic Line class, including better control over line width across different platforms.