Babylonjs Engine

# Babylon.js Real-World Examples

Comprehensive collection of production-ready Babylon.js patterns and implementations.

## Table of Contents

- [Model Loading & Optimization](#model-loading--optimization)
- [Advanced Materials](#advanced-materials)
- [Physics Simulations](#physics-simulations)
- [Particle Systems](#particle-systems)
- [Post-Processing Effects](#post-processing-effects)
- [GUI & User Interface](#gui--user-interface)
- [WebXR & VR](#webxr--vr)
- [Performance Optimization](#performance-optimization)
- [Camera Systems](#camera-systems)
- [Animation Patterns](#animation-patterns)

---

## Model Loading & Optimization

### GLTF Model Viewer with Progress

```javascript
import { SceneLoader } from '@babylonjs/core/Loading/sceneLoader.js';
import { Texture } from '@babylonjs/core/Materials/Textures/texture.js';
import { PBRMaterial } from '@babylonjs/core/Materials/PBR/pbrMaterial.js';
import '@babylonjs/loaders/glTF';

async function createModelViewer(scene, modelUrl, fileName) {
  // Show loading progress
  let loadingScreen = document.getElementById('loading');

  BABYLON.SceneLoader.OnPluginActivatedObservable.addOnce((loader) => {
    loader.onProgress = (event) => {
      const progress = event.lengthComputable
        ? (event.loaded / event.total) * 100
        : 0;

      if (loadingScreen) {
        loadingScreen.textContent = `Loading: ${progress.toFixed(0)}%`;
      }
    };
  });

  // Load model
  const result = await SceneLoader.ImportMeshAsync(
    null,
    modelUrl,
    fileName,
    scene
  );

  if (loadingScreen) {
    loadingScreen.style.display = 'none';
  }

  // Center model
  const meshes = result.meshes;
  const boundingBox = meshes[0].getHierarchyBoundingVectors();
  const center = BABYLON.Vector3.Center(boundingBox.min, boundingBox.max);

  meshes.forEach(mesh => {
    mesh.position.subtractInPlace(center);
  });

  // Scale to fit
  const size = boundingBox.max.subtract(boundingBox.min);
  const maxDimension = Math.max(size.x, size.y, size.z);
  const scale = 5 / maxDimension;

  result.meshes[0].scaling.scaleInPlace(scale);

  // Setup environment
  const envTexture = BABYLON.CubeTexture.CreateFromPrefilteredData(
    'https://assets.babylonjs.com/environments/environmentSpecular.env',
    scene
  );
  scene.environmentTexture = envTexture;

  // Apply PBR to all meshes
  meshes.forEach(mesh => {
    if (mesh.material && mesh.material.albedoTexture) {
      // Already has material, enhance it
      mesh.material.environmentIntensity = 1.0;
    } else if (!mesh.material) {
      // No material, create default
      const pbr = new PBRMaterial('defaultPBR', scene);
      pbr.metallic = 0.0;
      pbr.roughness = 0.5;
      pbr.baseColor = new BABYLON.Color3(0.8, 0.8, 0.8);
      mesh.material = pbr;
    }
  });

  return result;
}
```

### Optimized LOD (Level of Detail)

```javascript
async function createLODMesh(scene, highResUrl, medResUrl, lowResUrl) {
  // Load all LOD levels
  const highRes = await SceneLoader.ImportMeshAsync(null, '', highResUrl, scene);
  const medRes = await SceneLoader.ImportMeshAsync(null, '', medResUrl, scene);
  const lowRes = await SceneLoader.ImportMeshAsync(null, '', lowResUrl, scene);

  const mainMesh = highRes.meshes[0];
  const medMesh = medRes.meshes[0];
  const lowMesh = lowRes.meshes[0];

  // Add LOD levels
  mainMesh.addLODLevel(15, medMesh);   // Switch at 15 units
  mainMesh.addLODLevel(30, lowMesh);   // Switch at 30 units
  mainMesh.addLODLevel(50, null);      // Don't render beyond 50 units

  return mainMesh;
}
```

### Mesh Simplification

```javascript
async function simplifyMesh(mesh, quality = 0.5) {
  const simplified = await mesh.simplify(
    [
      { quality: quality, distance: 10 },
      { quality: quality * 0.5, distance: 25 },
      { quality: quality * 0.25, distance: 50 }
    ],
    true,  // parallelProcessing
    BABYLON.SimplificationType.QUADRATIC
  );

  return simplified;
}
```

### Batch Model Loading

```javascript
asy