ThreeJS Sprite Alignment Issue

Based on your description, you're experiencing perspective distortion with sprites when they're positioned away from the center of the viewport. This is a common issue when working with sprites in a 3D environment with perspective cameras.

Understanding the Issue

Sprites in ThreeJS are always facing the camera (billboarding), but they still exist in 3D space and are affected by perspective. When positioned away from the center of the view, perspective distortion can cause misalignment of your label group.

Potential Solutions

1. Use a Helper to Visualize Positioning
   You might benefit from using one of ThreeJS's helper classes to better understand the positioning:

   • AxesHelper to visualize the coordinate system
   • BoxHelper to see the bounding box of your sprite group

2. Adjust Sprite Scale Based on Distance
   Sprites don't automatically scale with distance. You might need to manually adjust their scale:

   JAVASCRIPTCopied
   // In your animation loop
   sprites.forEach(sprite => {
     // Calculate distance from camera
     const distance = sprite.position.distanceTo(camera.position);
     // Adjust scale based on distance
     sprite.scale.set(distance * 0.1, distance * 0.1, 1);
   });

3. Use CSS2DRenderer Instead
   For UI elements like labels that need to maintain consistent positioning regardless of perspective, consider using CSS2DRenderer which overlays HTML elements:

   JAVASCRIPTCopied
   import { CSS2DRenderer, CSS2DObject } from 'three/examples/jsm/renderers/CSS2DRenderer.js';
   
   // Setup CSS renderer alongside your WebGL renderer
   const labelRenderer = new CSS2DRenderer();
   labelRenderer.setSize(window.innerWidth, window.innerHeight);
   labelRenderer.domElement.style.position = 'absolute';
   labelRenderer.domElement.style.top = '0px';
   document.body.appendChild(labelRenderer.domElement);
   
   // Create label
   const div = document.createElement('div');
   div.textContent = 'Label';
   div.style.backgroundColor = 'rgba(255, 255, 255, 0.7)';
   div.style.padding = '2px';
   const label = new CSS2DObject(div);
   label.position.set(x, y, z);
   scene.add(label);
   
   // In animation loop
   labelRenderer.render(scene, camera);

4. Use an Orthographic Camera
   If your application allows it, using an orthographic camera eliminates perspective distortion:

   JAVASCRIPTCopied
   const camera = new THREE.OrthographicCamera(
     width / -2, width / 2, 
     height / 2, height / -2, 
     1, 1000
   );

Without seeing your specific implementation details, these are general approaches to address sprite alignment issues in ThreeJS. The most appropriate solution will depend on your specific requirements and constraints.