Camera Positioning for Orthographic Views in Three.js

Based on your description, you're trying to implement standard orthographic views (top, front, side, etc.) similar to CAD software. This is a common requirement in 3D visualization applications.

Understanding the Issue

Your problem stems from how camera positioning and targeting works in Three.js. When using controls like OrbitControls, the camera always looks at a target point (usually the scene center), which doesn't give you the precise orthographic views you need.

Solution Approach

To achieve CAD-like orthographic views, you need to:

1. Position the camera at the correct distance from the object
2. Set the correct camera orientation (up vector)
3. Point the camera directly at the object
4. Ensure the camera's view is perpendicular to the desired face

Here's how you can implement this:

JAVASCRIPTCopied
function setStandardView(viewType, object) {
  // Get the object's bounding box to determine size and position
  const boundingBox = new THREE.Box3().setFromObject(object);
  const center = boundingBox.getCenter(new THREE.Vector3());
  const size = boundingBox.getSize(new THREE.Vector3());
  
  // Calculate appropriate distance based on object size
  const maxDim = Math.max(size.x, size.y, size.z);
  const distance = maxDim * 2; // Adjust multiplier as needed
  
  // Set camera position and orientation based on view type
  switch(viewType) {
    case 'front':
      camera.position.set(center.x, center.y, center.z + distance);
      camera.up.set(0, 1, 0);
      break;
    case 'back':
      camera.position.set(center.x, center.y, center.z - distance);
      camera.up.set(0, 1, 0);
      break;
    case 'left':
      camera.position.set(center.x - distance, center.y, center.z);
      camera.up.set(0, 1, 0);
      break;
    case 'right':
      camera.position.set(center.x + distance, center.y, center.z);
      camera.up.set(0, 1, 0);
      break;
    case 'top':
      camera.position.set(center.x, center.y + distance, center.z);
      camera.up.set(0, 0, 1);
      break;
    case 'bottom':
      camera.position.set(center.x, center.y - distance, center.z);
      camera.up.set(0, 0, -1);
      break;
  }
  
  // Point camera at the center of the object
  camera.lookAt(center);
  
  // If using controls, update them
  if (controls) {
    controls.target.copy(center);
    controls.update();
  }
}

Additional Considerations

1. If you're using OrbitControls, you'll need to update the controls.target to match the object's center:

JAVASCRIPTCopied
controls.target.copy(center);
controls.update();

2. For a smoother transition between views, consider using a tweening library:

JAVASCRIPTCopied
// Example with GSAP or similar tweening library
function animateToView(viewType, object) {
  // Calculate target position and orientation
  const targetPosition = new THREE.Vector3();
  const targetUp = new THREE.Vector3();
  // ... set these based on viewType ...
  
  // Animate the camera
  gsap.to(camera.position, {
    x: targetPosition.x,
    y: targetPosition.y,
    z: targetPosition.z,
    duration: 1,
    onUpdate: function() {
      camera.lookAt(center);
      controls.update();
    }
  });
  
  gsap.to(camera.up, {
    x: targetUp.x,
    y: targetUp.y,
    z: targetUp.z,
    duration: 1
  });
}

3. For precise orthographic views, consider using an OrthographicCamera instead of PerspectiveCamera, as it will give you true parallel projections like in CAD software.

This approach should help you achieve the desired CAD-like orthographic views of your objects, regardless of their position in the scene.