Difference Between Clone and Copy in Three.js Vector3

When working with 3D graphics in Three.js, managing memory and performance is crucial. This article explains the fundamental differences between the .clone() and .copy() methods when duplicating Vector3 instances, helping you write more efficient WebGL code by understanding when to instantiate new objects versus when to reuse existing ones.

The clone() Method

The .clone() method creates a brand new instance of a Vector3 and copies the x, y, and z values of the original vector into this new object.

Syntax and Example

const original = new THREE.Vector3(1, 2, 3);

// Creates a new Vector3 object in memory
const duplicated = original.clone(); 

When to Use clone()

Use .clone() when you need to duplicate a vector and do not have an existing vector object ready to receive the values. It is highly convenient for one-off operations outside of performance-critical loops.

The copy() Method

The .copy() method does not create a new object. Instead, it copies the x, y, and z values from a source vector into an already existing Vector3 instance.

Syntax and Example

const original = new THREE.Vector3(1, 2, 3);
const target = new THREE.Vector3(); // Already instantiated

// Copies values from original into target without creating a new object
target.copy(original); 

When to Use copy()

Use .copy() when you already have an instantiated vector that you want to overwrite. This is the preferred method for performance-critical code.

Key Differences

Performance Implications in the Render Loop

The choice between .clone() and .copy() is especially important inside the Three.js animation/render loop (requestAnimationFrame).

If you use .clone() inside a render loop that runs 60 times per second, you will generate thousands of temporary objects. This triggers Web browser Garbage Collection (GC). When the browser pauses execution to clean up these discarded objects, it causes micro-stutters (frame drops) in your 3D animation.

Bad Practice (Inside Render Loop)

function animate() {
    requestAnimationFrame(animate);

    // BAD: Creates a new object every frame, leading to GC lag
    const temporaryPosition = mesh.position.clone().addScalar(5);
    camera.lookAt(temporaryPosition);
}

Good Practice (Inside Render Loop)

To optimize performance, instantiate a global or scoped helper vector once, and reuse it inside the loop using .copy().

// Instantiate once outside the loop
const tempPosition = new THREE.Vector3();

function animate() {
    requestAnimationFrame(animate);

    // GOOD: Reuses the existing memory address
    tempPosition.copy(mesh.position).addScalar(5);
    camera.lookAt(tempPosition);
}