Reducing Input Latency in Three.js Applications

Reducing input latency below the typical 10-30ms range in web browsers is challenging but there are some approaches you can consider for Three.js applications.

Potential Approaches

Your ideas are on the right track. Here are some thoughts on each approach and additional considerations:

Web HID API

This can provide more direct access to input devices, potentially bypassing some browser input processing. However, browser support is still limited and it may not completely eliminate the inherent browser input delay.

Web Worker + SharedArrayBuffer

This approach can help by:

• Moving heavy calculations off the main thread
• Using SharedArrayBuffer for zero-copy communication between threads
• Allowing input processing to happen in parallel with rendering

Animation Loop Optimization

The Three.js animation loop is where you'll want to focus. Consider using the Timer class (an alternative to Clock) which has better design for consistent time calculations:

JAVASCRIPTCopied
import { Timer } from 'three/examples/jsm/misc/Timer.js';

const timer = new Timer();

function animate() {
  requestAnimationFrame(animate);
  timer.update();
  
  // Use timer.getDelta() for consistent time values
  // Process input and update scene here
  
  renderer.render(scene, camera);
}

Input Handling Techniques

1. Predictive Input Processing: Implement input prediction to estimate where objects should be between frames

2. Input Buffering: Store input events with timestamps and process them at the earliest possible moment in your render loop

3. Direct requestAnimationFrame Binding: Attach your input handlers directly to the animation frame cycle

JAVASCRIPTCopied
let keys = {};

window.addEventListener('keydown', (e) => {
  keys[e.code] = true;
});

window.addEventListener('keyup', (e) => {
  keys[e.code] = false;
});

function animate() {
  requestAnimationFrame(animate);
  
  // Process input at the beginning of each frame
  processInput(keys);
  
  renderer.render(scene, camera);
}

Additional Considerations

• Use performance.now() for high-precision timing
• Consider using pointer events with the { passive: true } option for touch input
• Minimize other main thread work that could cause jank
• Ensure your rendering pipeline is optimized (use BufferGeometryUtils where appropriate)

While getting below 10ms consistently may be difficult due to browser and OS constraints, these techniques should help minimize the perceived latency in your Three.js application.