When you use Three.js within a React application, it is essential to understand how to integrate Three.js scenes into React's component lifecycle. React components have a lifecycle that includes mounting (when a component is added to the DOM), updating, and unmounting (when a component is removed from the DOM). To create a Three.js scene, you typically initialize the renderer, scene, camera, and other objects inside a React component when it mounts. You also attach the renderer's output (a canvas element) to a DOM node managed by React.

When your component mounts, you set up the Three.js scene and start any animation loops or rendering processes. This setup ensures the 3D content appears as soon as the component is rendered. However, it's just as important to handle the unmounting phase properly. When a component is about to unmount, you need to stop any ongoing animations, remove event listeners, and dispose of all Three.js objects and resources. Failing to do so can lead to memory leaks, performance issues, and unexpected behavior, especially in single-page applications where components may be mounted and unmounted frequently.

A key best practice is to always clean up Three.js resources in the component's unmount phase. This means explicitly disposing of geometries, materials, textures, and renderers. You should also cancel any animation frames and remove event listeners or observers that were added during the component's lifecycle. By following these practices, you ensure that your React app remains performant and stable, even as users navigate between different views or interact with dynamic 3D content.

Proper resource cleanup and memory management are crucial when using Three.js in React applications. Three.js can allocate significant resources for 3D objects, textures, and animations, and if these resources are not released when a component unmounts, your app's memory usage will increase over time. This can slow down your app, cause crashes, or lead to rendering glitches. To avoid these issues, always dispose of all Three.js objects and cancel any running animation loops or timers in the component's cleanup phase. This approach not only prevents memory leaks but also helps maintain smooth performance and reliability across your app.