Updating Material Colors in Three.js

There are a few issues with your current approach. When using scene.traverse(), you don't need an additional loop inside the callback function. The traverse() method already iterates through all objects in the scene hierarchy for you.

Here's the correct way to change the color of materials for all objects in your scene:

JAVASCRIPTCopied
function multico() {
    scene.traverse(function(object) {
        // Check if the object has a material property
        if (object.material) {
            // Handle objects with a single material
            if (object.material.color) {
                object.material.color.set(Math.random() * 0xffffff);
            }
            
            // Handle objects with multiple materials (material array)
            else if (Array.isArray(object.material)) {
                object.material.forEach(material => {
                    if (material.color) {
                        material.color.set(Math.random() * 0xffffff);
                    }
                });
            }
        }
    });
}

Key points to note:

1. The traverse() method already loops through all objects in the scene
2. Not all objects have materials (like cameras, lights, etc.)
3. Some objects might have an array of materials instead of a single material
4. Not all materials have a color property (like ShaderMaterial)

If you're specifically targeting objects from a GLTF model, you might want to add additional checks:

JAVASCRIPTCopied
function multico() {
    scene.traverse(function(object) {
        // Check if it's a mesh object
        if (object.isMesh) {
            // Handle single material
            if (object.material) {
                if (object.material.color) {
                    object.material.color.set(Math.random() * 0xffffff);
                    // If you need to update the material, mark it for update
                    object.material.needsUpdate = true;
                }
            }
        }
    });
}

This approach should correctly update the color of all applicable materials in your scene when the function is called.