Texture Loss in Three.js iOS Application

Based on your description, it sounds like you're experiencing a WebGL context loss issue when your app returns from background on iOS. This is a common problem when developing WebGL applications for mobile platforms.

Possible Causes

When your app goes to the background on iOS, the WebGL context might be lost, and textures may not be properly restored when the app returns to the foreground. This is particularly common with GLB models that use complex textures.

Potential Solutions

Here are some approaches you might try:

1. Handle WebGL Context Loss: Implement event listeners for context loss and restoration:

JAVASCRIPTCopied
const renderer = new THREE.WebGLRenderer();
renderer.domElement.addEventListener('webglcontextlost', handleContextLost, false);
renderer.domElement.addEventListener('webglcontextrestored', handleContextRestored, false);

function handleContextLost(event) {
  event.preventDefault();
  console.log('WebGL context lost');
}

function handleContextRestored() {
  console.log('WebGL context restored');
  // Reload your textures and materials here
}

2. Force Texture Reload: When your app returns from background, you might need to explicitly reload the textures for your GLB model:

JAVASCRIPTCopied
// When app returns from background
function onAppResume() {
  // For each material in your GLB model
  yourGlbModel.traverse((child) => {
    if (child.isMesh && child.material) {
      if (Array.isArray(child.material)) {
        child.material.forEach(mat => {
          if (mat.map) {
            mat.map.needsUpdate = true;
          }
        });
      } else if (child.material.map) {
        child.material.map.needsUpdate = true;
      }
    }
  });
  
  // Force renderer update
  renderer.forceContextLoss();
  // You might need to reinitialize the renderer here
}

3. Use Capacitor App Lifecycle Events: Implement handlers for app state changes:

JAVASCRIPTCopied
import { App } from '@capacitor/app';

App.addListener('appStateChange', ({ isActive }) => {
  if (isActive) {
    // App has come to the foreground
    // Reload textures or reinitialize renderer if needed
  }
});

4. Texture Caching: Ensure your textures are properly cached and can be reloaded:

JAVASCRIPTCopied
// Store references to your important textures
const textureCache = {};

function loadTexture(url, onLoad) {
  const textureLoader = new THREE.TextureLoader();
  const texture = textureLoader.load(url, (loadedTexture) => {
    textureCache[url] = loadedTexture;
    if (onLoad) onLoad(loadedTexture);
  });
  return texture;
}

function reloadTextures() {
  Object.keys(textureCache).forEach(url => {
    textureCache[url].needsUpdate = true;
  });
}

I hope one of these approaches helps resolve your issue. The key is properly handling the WebGL context loss and ensuring textures are correctly reloaded when your app returns to the foreground.